Electronic Terms Glossary

Term	Definition
A	Abbreviation for "ampere," a unit of electrical current.
Absorption	Loss or dissipation of energy as it travels through a medium. Example: radio waves lose some of their energy as they travel through the atmosphere.
AC	Abbreviation for "alternating current."
Acceptor Atoms	Trivalent atoms that accept free electrons from pentavalent atoms.
AC Coupling	Circuit that passes an AC signal while blocking a DC voltage.
AC/DC	Equipment that will operate on either an AC or DC power source.
AC Generator	Device used to transform mechanical energy into AC electrical power.
AC Load Line	A graph representing all possible combinations of AC output voltage and current for an amplifier.
AC Power Supply	Power supply that delivers an AC voltage.
Active Component	A component that changes the amplitude of a signal between input and output.
Active Filter	A filter that uses an amplifier in addition to reactive components to pass or reject selected frequencies.
Active Region	The region of BJT operation between saturation and cutoff used for linear amplification.
AC Voltage	A voltage in which the polarity alternates.
ADC	Abbreviation for "analog to digital converter."
Admittance	(symbol "Y") Measure of how easily AC will flow through a circuit. Admittance is the reciprocal of impedance and is measured in siemens.
AF	Abbreviation for "audio frequency."
AFC	Abbreviation for "automatic frequency control."
AGC	Abbreviation for "automatic gain control."
Alkaline Cell	A primary cell that delivers more current than a carbon-zinc cell. Also known as an "alkaline manganese cell."
Alligator Clip	Spring clip on the end of a test lead used to make a temporary connection.
Alpha	Ratio of collector current to emitter current in a bipolar junction transistor (BJT). Greek letter a is the symbol used.
Alternating Current	An electric current that rises to a maximum in one direction, falls back to zero, and then rises to a maximum in the opposite direction and then repeats.
Alternator	Name for an AC generator.
AM	Abbreviation for "amplitude modulation."
Ammeter	A meter used to measure current.
Ampere	Unit of electrical current.
Amplifier	A circuit that increases the voltage, current, or power of a signal.
Amplitude	Magnitude or size of a signal voltage or current.
Analog	Information represented as continously varying voltage or current rather than in discrete levels as opposed to digital data varying between two discrete levels.
Anode	The positive electrode or terminal of a device. The "P" material of a diode.
Antenna, Transmitting	A device that converts an electrical wave into an electromagnetic wave that radiates away from the antenna.
Antenna, Receiving	A device that converts a radiated electromagnetic wave into an electrical wave.
Apparent Power	Power attained in an AC circuit as a product of effective voltage and current that reach their peak at different times.
Arc	Discharge of electricity through a gas such as lightning discharging through the atmosphere.
Armature	The rotating or moving component of a magnetic circuit.
Armstrong Oscillator	An oscillator that uses an isolation transformer to achieve positive feedback from output to input.
Astable Multivibrator	An oscillator that produces a square wave output from a DC voltage.
Atom	The smallest particle that an element can be broken down into and still maintain its unique identity.
Atomic Number	The number of positive charges or protons in the nucleus of an atom.
Attenuate	To reduce the amplitude of an action or signal. The opposite of amplification.
Audio	Relating to frequencies that can be heard by the human ear. Approximately 20 Hz to 20 kHz.
Autotransformer	A single winding transformer where the output is taken from taps on the winding.
Average Value	A value of voltage or current where the area of the wave above the value equals the area of the wave below the value.
AVC	Abbreviation for "automatic volume control."
Avionics	Aviation electronics.
AWG	Abbreviation for "american wire gauge." A gauge that assigns a number value to the diameter of a wire.
Balanced Bridge	Condition that occurs when a bridge circuit is adjusted to produce a zero output.
Band-pass Filter	A tuned circuit designed to pass a band of frequencies between a lower cut-off frequency (f₁) and a higher cut-off frequency (f₂). Frequencies above and below the pass band are heavily attenuated.
Band-stop Filter	A tuned circuit designed to stop frequencies between a lower cut-off frequency (f₁) and a higher cut-off frequency (f₂) of the amplifier while passing all other frequencies.
Bandwidth	Width of the band of frequencies between the half power points.
Barrier Potential	The natural difference of potential that exists across a forward biased PN junction.
Base	The region that lies betwen the emitter and collector of a bipolar junction transistor (BJT).
Base Biasing	A method of biasing a BJT in which the bias voltage is supplied to the base by means of a resistor.
Battery	A DC voltage source containing two or more cells that convert chemical energy to electrical energy.
Baud	A unit of signaling speed equal to the number of signal events per second. Not necessarily the same as bits per second.
Beta	b; The ratio of collector current to base current in a bipolar junction transistor (BJT).
Bias	A DC voltage applied to a device to control its operation.
Binary	A number system having only two symbols, 0 and 1. A base 2 number system.
Bipolar Junction Transistor (BJT)	A three-terminal device in which emitter to collector current is controlled by base current.
Bistable Multivibrator	A multivibrator with two stable states. An external signal is required to change the output from one state to the other. Also called a latch.
Bleeder Current	A current drawn continously from a souce. Bleeder current is used to stabilize the output voltage of a source.
Bode Plot	A graph of gain versus frequency.
Branch Current	The portion of total current flowing in one path of a parallel circuit.
Breakdown Voltage	Voltage at which the breakdown of a dielectric or insulator occurs.
Breakover Voltage	Minimum voltage required to cause a diac to break down and conduct.
Bridge Rectifier	A circuit using four diodes to provide full wave rectification. Converts an AC voltage to a pulsating DC voltage.
Buffer	An amplifier used to isolate a load from a source.
Bulk Resistance	The natural resistance of a P type or N type semiconductor material.
Butterworth Filter	A type of active filter characterized by a constant gain (flat response) across the midband of the circuit and a 20-dB-per-decade roll-off rate for each pole contained in the circuit.
BW	Abbreviation for bandwidth.
Bypass Capacitor	A capacitor used to provide an AC ground at some point in a circuit.
Byte	Group of eight binary digits or bits.
Cable	Group of two or more insulated wires.
CAD	Abbreviation for "computer aided design."
Calibration	To adjust the correct value of a reading by comparison to a standard.
Capacitance	The ability of a capacitor to store an electrical charge. The basic unit of capacitance is the Farad.
Capacitive Reactance	The opposition to current flow provided by a capacitor. Capacitive reactance is measured in ohms and varies inversly with frequency.
Capacitor	An electronic component having capacitive reactance.
Capacitor Microphone	Microphone whose operation depends on variations in capacitance caused by varying air pressure on the movable plate of a capacitor.
Carbon-film Resistor	Device made by depositing a thin carbon film on a ceramic form.
Carbon Microphone	Microphone whose operation depends on pressure variation in carbon granules causing a change in resistance.
Carbon Resistor	Resistor of fixed value made by mixing carbon granules with a binder which is moulded and then baked.
Cascaded Amplifier	An amplifier with two or more stages arranged in a series configuration.
Cascode Amplifier	A high-frequency amplifier made up of a common-source amplifier with a common-gate amplifier in its drain network.
Cathode	The negative terminal electrode of a device. The N material in a junction diode.
Cathode Ray Tube (CRT)	Vacuum tube used to display data in a visual form. Picture tube of a television or computer terminal.
Cell	Single unit used to convert chemical energy into a DC electrical voltage.
Center Frequency	Frequency to which an amplifier is tuned. The frequency halfway between the cut-off frequencies of a tuned circuit.
Center Tap	Midway connection between the two ends of a winding.
Center Tapped Rectifier	Circuit that make use of a center tapped transformer and two diodes to provide full wave rectification.
Center Tapped Transformer	A transformer with a connection at the electrical center of a winding.
Ceramic Capacitor	Capacitor in which the dielectric is ceramic.
Charge	Quantity of electrical energy.
Charge Current	Current that flows to charge a capacitor or battery when voltage is applied.
Chassis	Metal box or frame into which components are mounted.
Chassis Ground	Connection to a chassis.
Chebyshev Filter	A type of active filter characterized by high roll-off rates (40 dB per decade per pole) and midband gain that is not constant.
Choke	Inductor used to oppose the flow of alternating current.
Circuit	Interconnection of components to provide an electrical path between two or more components.
Circuit Breaker	A protective device used to open a circuit when current exceeds a maximum value. In effect, a reusable fuse.
Clamper	A diode circuit used to change the DC level of a waveform without distorting the waveform.
Clapp Oscillator	A variation of the Colpitts oscillator. An added capacitor is used to eliminate the effects of stray capacitance on the operation of the basic Colpitts oscillator.
Class A Amplifier	A linear amplifier biased so the active device conducts through 360 degrees of the input waveform.
Class B Amplifier	An amplifier with two active devices. The active components are biased so that each conducts for approximately 180 degrees of the input waveform cycle.
Class C Amplifier	An amplifier in which the active device conducts for less than 180 degrees of the input waveform cycle.
Clipper	A diode circuit used to eliminate part of a waveform.
Clipping	Distortion caused by overdriving an amplifier.
Clock	A square waveform used for synchronizing and timing of several circuits.
Cosed Circuit	Circuit having a complete path for current flow.
Closed-Loop Gain	Gain of an amplifier when a feedback path is present.
Coaxial Cable	Transmission line in which the signal carrying conductor is covered by a dielectric and another conductor.
Coefficient of Coupling	The degree of coupling between two circuits.
Coercive Force (H)	Magnetizing force needed to reduce residual magnetism in a material to zero.
Collector	The semiconductor region in a bipolar junction transistor through which a flow of charge carriers leaves the base region.
Collector Characteristic Curve	A graph of collector voltage over collector current for a given base current.
Color Code	Set of colors used to indicate value of a component.
Colpitts Oscillator	An oscillator with a pair of tapped capacitors in the feedback network.
Common-Anode Display	A multisegment light emitting diode (LED) with a single positive voltage input connection. Separate cathode connections are provided for each individual segment.
Common Cathode Display	A multisegment light emitting diode (LED) with a single negative voltage input connection. Separate anode connections are provided for each individual segment.
Common Base Amplifier	A BJT circuit in which the base connection is common to both input and output.
Common Collector Amplifier	A BJT circuit in which the collector connection is common to both input and output.
Common Drain Amplifier	An FET circuit in which the drain connection is common to both input and output.
Common Emitter Amplifier	A BJT circuit in which the emitter connection is common to both input and output.
Common Gate Amplifier	An FET circuit in which the gate connection is common to both input and output.
Common Source Amplifier	An FET circuit in which the source connection is common to both input and output.
Common-Mode Rejection Ratio (CMRR)	The ratio of op-amp differential gain to common-mode gain. A measure of an op-amp's ability to reject common-mode signals such as noise.
Common-Mode Signals	Signals that appear simultaneously at two inputs of an operational amplifier (op-amp). Common mode signals are always equal in amplitude and phase.
Comparator	An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs.
Complementary Symmetry Amplifier	A class B amplifier using matched complementry transistors. Does not require a phase inverter for push-pull output.
Complementry Transistors	Two transistors, one NPN and one PNP, having near identical charastics. N-channel and P-channel FETs can also be complementry.
Complex Numbers	Numbers composed of a real number part and an imaginary number part.
Compliance	The maximum possible peak-to-peak output of an amplifier.
Constant Current Circuit	Circuit used to maintain constant current to a load having resistance that changes.
Contact	Current carrying part of a switch, relay or connector.
Continuity	Occurs when a complete path for current exists.
Conventional Current Flow	Concept of current produced by the movement of positive charges towards the negative terminal of a source.
Copper Loss	Power lost in transformers, generators, connecting wires and other parts of a circuit due to current flow through the resistance of copper conductors.
Core	Magnetic material within a coil used to concentrate the magnetic field.
Coulomb	Unit of electric charge. A negative coulomb charge consists of 6.24 x 10¹⁸ electrons.
Counter Electro-motive Force (Counter EMF)	Voltage induced into an inductor due to an alternating or pulsating current. Counter emf is always in polarity opposite to that of the applied voltage. Opposing a change of current.
Coupling	To electronically connect two circuits so that signal will pass from one to the other.
Covalent Bond	The way some atoms complete their valence shells by sharing valence electrons with neighboring atoms.
Crossover Distortion	Distortion caused by both devices in a class B amplifier being cut off at the same time.
Crowbar	Circuit used to protect the output of a souce from a short circuited load. Load current is limited to a value the source can deliver without damage.
CRT	Abbreviation for "cathode ray tube."
Crystal	Natural or synthetic piezoelectric or semiconductor material with atoms arranged with some degree of geometric regularity.
Crystal-Controlled Oscillator	Oscillator that uses a quartz crystal in its feedback path to maintain a stable out-put frequency.
Current	Measured in amperes, it is the flow of electrons through a conductor. Also know as electron flow.
Current Amplifier	Amplifier to increase signal current.
Current Divider	Parallel network designed to divide the total current of a circuit.
Current Feedback	Feedback configuration where a portion of the output current is fed back to the amplifier input.
Current-Limiting Resistor	Resistor in the path of current flow to control the amount of current drawn by a device.
Current Mirror	Term used to describe the fact that DC current through the base circuit of a class B amplifier is approximately equal to the DC collector current.
Cutoff	Condition when an active device is biased such that output current is near zero or beyond zero.
Cutoff Frequency	Frequency at which the power gain of an amplifier falls below 50% of maximum.
Cycle	When a repeating wave rises from zero to a positive maximum then back to zero and on to a negative maximum and back to zero it is said to have completed one cycle.
DAC	Abbreviation for "digital to analog converter."
Damping	Reduction in magnitude of oscillation due to energy being dissipated as heat.
Darlington Pair	An amplifier consisting of two bipolar junction transistors with their collectors connected together and the emitter of one connected to the base of the other. Circuit has an extremely high current gain and input impedance.
DC	Abbreviation for "direct current."
DC Load Line	A graph representing all possible combinations of voltage and current for a given load resistor in an amplifier.
DC Offset	The change in input voltage required to produce a zero output voltage when no signal is applied to an amplifier.
DC Power Supply	Any source of DC power for electrical equipment.
Dead Short	Short circuit having zero resistance.
Decade	A frequency factor of ten.
Decibel (dB)	A logarithmic representation of gain or loss.
Degenerative Feedback	Also called negative feedback. A portion of the output of an amplifier is inverted and connected back to the input. This controls the gain of the amplifier and reduces distortion and noise.
Delay Time	The time for collector current to reach 10% of its maximum value in a BJT switching circuit.
Depletion Region	The area surrounding a pn junction that is depleted of carriers.
Depletion Mode	In an FET, an operating mode where reverse gate-source voltage is used to deplete the channel of free carriers. This reduces the size of the channel and increases its resistance.
Depletion-Mode MOSFET	A MOSFET designed to operate in either depletion mode or enhancement mode.
Device	A component or part.
Diac	A two terminal bidirectional thyristor. Has a symmetrical switching mode.
Dielectric	Insulating material between two plates where an electrostatic field exists.
Dielectric Constant	Peoperty of a material that determines how much electrostatic energy can be stored per unit volume when unit voltage is applied.
Dielectric Strength	The maximum voltage an insulating material can withstand without breaking down.
Differential Amplifier	An amplifier in which the output is in proportion to the differences between voltages applied to its two inputs.
Differentiator	A circuit in which the output voltage is in proportion to the rate of change of the input voltage. A high-pass RC circuit.
Diffusion	Tendency of conduction band electrons to wander across a pn junction to combine with valence band holes.
Digital	Relating to devices or circuits that have outputs of only two discrete levels. Examples: 0 or 1, high or low, on or off, true or false.
Diode	A two-terminal device that conducts in only one direction.
DIP	Abbreviation for "dual in-line package."
Direct Coupling	Where the output of an amplifier is connected directly to the input of another amplifier or to a load. Also known as DC coupling because DC signals are not blocked.
Direct Current	Current that flows in only one direction.
Discharge	Release of energy stored in either a battery or a capacitor.
Discrete Component	Package containing only a single component as opposed to an integrated circuit containg many components in a single package.
Dissipation	Release of electrical energy in the form of heat.
Distortion	An undesired change in a waveform or signal.
Distributed Capacitance	Any capacitance other than that within a capacitor. For example, the capacitance between adjacent turns of wire in a coil.
Distributed Inductance	Any inductance other than that within an inductor. Example: inductance in any conductor.
Domain	A moveable magnetized area in a magnetized material. Also known as magnetic domain.
Donor Atoms	Pentavalent atoms that give up electrons to the conduction band in an N-type semiconductor material.
Doping	The process of adding impurity atoms to intrinsic (pure) silicon or germanium to improve the conductivity of the semiconductor material.
Dot Convention	Standard used with transformer symbols to indicate whether the secondary voltage is in phase or out of phase with the primary voltage.
Drift	A problem that can develop in tuned amplifiers when the frequency of the tuned circuit changes due to temperature or component aging.
Dropping Resistor	Resistor whose value has been chosen to drop or develop a given voltage.
Dry Cell	DC voltage generating chemical cell using a non liquid (paste) electrolyte.
Dual In-Line Package	Integrated circuit package having two rows of connecting pins.
Dual Trace Oscilloscope	Oscilloscope that can simultaneously display two signals.
Dynamic	Relating to conditions that are changing or in motion.
E-core	Laminated form in the shape of the letter "E," onto which inductors and transformers are wound.
Eddy Currents	Currents induced into a conducting core due to the changing magnetic field. Eddy currents produce heat which is a loss of power and lowers the efficiency of an inductor.
Efficiency	The amount of power delivered to the load of an amplifier as a percentage of the power required from the power supply.
Electric Charge	Electric energy stored on the surface of a material. Also known as a static charge.
Electric Field	A field or force that exists in the space between two different potentials or voltages. Also known as an electrostatic field.
Electricity	Science states that certain particles possess a force field or charge. The charge possessed by an electron is negative while the charge possessed by a proton is positive. Electricity can be divided into two groups, static and dynamic. Static electricty deals with charges at rest and dynamic electricity deals with charges in motion.
Electric Polarization	A displacement of bound charges in a dielectric when placed in an electric field.
Electroacoustic Transducer	Device that produces an energy transfer from electric to acoustic (sound) or from acoustic to electric. Examples include a microphone, earphones, and loud speakers.
Electroluminescence	Conversion of electrical energy into light energy.
Electrolyte	Electrically conducting liquid (wet) or paste (dry).
Electrolytic Capacitor	A capacitor having an electrolyte between the two plates. A thin layer of oxide is deposited on only the positive plate. The oxide acts as the dielectric for the capacitor. Electrolytic capacitors are polarized and so must be connected in correct polarity to prevent breakdown.
Electromagnet	A coil of wire usually wound on a soft iron or steel core. When current is passed through the coil, a magnetic field is generated. The core provides an easy path for the magnetic lines of force. This concentrates the field in the core.
Electromagnetic Communication	Use of an electromagnetic wave to pass information between two points. Also called wireless communication.
Electromagnetic Induction	Voltage produced in a coil due to relative motion between the coil and magnetic lines of force.
Electromagnetic Spectrum	List or diagram showing the range of electromagnetic radiation.
Electromagnetic Wave	Wave that consists of both electric and magnetic variation.
Electromagnetism	Relates to the magnetic field generated around a conductor when current is passed through it.
Electromechanical Transducer	Device that transforms electrical energy into mechanical energy (electric motor) or mechanical energy into electrical energy (generator).
Electromotive Force (EMF)	Force that causes the motion of electrons due to potential difference between two points. (voltage)
Electron	Smallest subatomic particle of negative charge that orbits the nucleus of an atom.
Electron Flow	Electrical current produced by the movement of free electrons toward a positive terminal.
Electrostatic	Related to static electric charge.
Electrostatic Field	Force field produced by static electrical charges.
Emitter	The semiconductor region from which charge carriers are injected into the base of a bipolar junction transistor.
Emitter Feedback	Coupling from the emitter output to the base input of a bipolar junction transistor.
Emitter Follower	A common collector amplifier. Has a high current gain, high input impedance, and low output impedance.
Energized	Being electrically connected to a voltage source so the device is activated.
Energy	Capacity to do work.
Engineering Notation	A floating point system in which numbers are expressed as products consisting of a number greater than one multiplied by an appropriate power of 10 that is some multiple of 3.
Enhancement-Mode MOSFET	A field effect transistor in which there are no charge carriers in the channel when the gate source voltage is zero.
Equivalent Resistance	Total resistance of all the individual resistances in a circuit.
Fall Time	Time it takes the falling edge of a pulse to go from 90% of peak voltage to 10% of peak voltage.
Farad	The basic unit of capacitance.
Feedback	A portion of the output signal of an amplifier that is connected back to the input of the same amplifier.
Feedback Amplifier	An amplifier with an external signal path from its output back to its input.
Ferrite	A powdered, compressed, and sintered magnetic material having high resistivity. The high resistance makes eddy current losses low at high frequencies.
Ferrite Bead	Ferrite composition in the form of a bead. Running a wire through the bead increases the inductance of the wire.
Ferrite-Core Inductor	An inductor wound on a ferrite core.
Ferrites	Compound composed of iron oxide, a metallic oxide, and ceramic. The metal oxides include zinc, nickel, cobalt, or iron.
Ferrous	Composed of and or containing iron. A ferrous metal exhibits magnetic characteristics as opposed to nonferrous material.
Fiber Optics	Laser's light output carries information that is conveyed between two points by thin glass optical fibers.
Field Effect Transistor (FET)	A voltage controlled transistor in which the source to drain conduction is controlled by gate to source voltage.
Filament	Thin thread of carbon or tungsten which produces heat or light with the passage of current.
Filter	Network consisting of capacitors, resistors and/or inductors used to pass certain frequencies and block others.
Flip Flop	A bistable multivibrator. A circuit which has two output states and is switched from one to the other by means of an external signal (trigger).
Floating Ground	Conmmon connection in a circuit that provides a return path for current but is not connected to an earth ground.
Flow Soldering	Flow or wave soldering technique in large scale electronic assembly to solder all the connections on a printed circuit board by moving the board over a wave of molten solder.
Flux	Material used to remove oxide films from the surface of metals in preparation for soldering.
Flux	In magnetism, the magnetic field consisting of lines of force.
Flux Density	The concentration of magnetic lines of force. Determines strength of the magnetic field.
Flywheel Effect	Sustaining effect of oscillation in an LC circuit.
Forward Bias	A PN junction bias which allows current to flow through the junction. Forward bias decreases the resistance of the depletion layer.
Free Electrons	Electrons that are not in any orbit around a nucleus.
Free Runing Multivibrator	A multivibrator that produces a continuous output waveform without any signal input. A square wave generator used to produce a clock signal.
Frequency	Rate of recurrence of a periodic wave. Measured in Hertz (cycles per second).
Frequency-Division Multiplex (FDM)	Transmission of two or more signals over a common path by using a different frequency band for each signal.
Frequency-Domain Analysis	A method of representing a waveform by plotting its amplitude against frequency.
Frequency Meter	Meter used to measure frequency of periodic waves.
Frequency Multiplier	A harmonic conversion circuit in which the frequency of the output signal is an exact multiple of the input frequency.
Frequency Response	Indication of how well a circuit responds to different frequencies applied to it.
Frequency Response Curve	A graph of amplitude over frequency indicating a circuit response to different frequencies.
Full-Scale Deflection	(FDS) Deflection of a meter's pointer to the farthest position on the scale.
Full-Wave Rectifier	Rectifier that makes use of the full AC wave in both the positive and negative half cycles.
Function Generator	Signal generator that can produce sine, square, triangle, and sawtooth output waveforms.
Fundamental Frequency	Lowest frequency in a complex waveform.
Fuse	A protective device in the current path that melts or breaks when current exceeds a predetermined maximum value.
Gain	Increase in voltage, current and/or power. Gain is expressed as a ratio of amplifier output value to the corresponding amplifier input value.
Gain Bandwidth Product	A device parameter that indicates the maximum possible product of gain and bandwidth. The gain bandwidth product of a device is equal to the unity gain frequency (f_unity) of the device.
Gamma Rays	High-frequency electromagnetic radiation from radio active particles.
Ganged	Mechanical coupling of two or more capacitors, switches, potentiometers, or any other adjustable components so that adjusting one control will operate all.
Gas	Any aeriform or completely elastic fluid which is not a solid or a liquid. Gasses are produced by heating a liquid beyond its boiling point.
Geiger Counter	Device used to detect nuclear particles.
Generator	Device used to convert mechanical energy to electrical energy.
Giga	Metric prefix for 1 billion (10⁹).
Ground	An intentional or accidental conducting path between an electrical system or circuit and the earth or some conducting body acting in place of the earth. A ground is often used as the common wiring point or reference in a circuit.
Gunn Diode	A semiconductor diode that utilizes the Gunn effect to produce microwave frequency oscillation or to amplify a microwave frequency signal.
H-Parameters	(hybrid parameters) Transistor specifications that describe the component operating limits under specific circumstances.
Half Power Point	A frequency at which the power is 50% of maximum. This corresponds to 70.7% of maximum current or voltage.
Half Wave Rectifier	A diode rectifier that converts AC to pulsating DC by eliminating either the negative or the positive alternation of each input AC cycle.
Harmonic	Sine wave that is smaller in amplitude and some multiple of a fundamental frequency. Example: 880 Hz is the second harmonic of 440 Hz, 880 Hz is the third harmonic of 220 Hz.
Hartley Oscillator	An oscillator that uses a tapped inductor in the feedback network.
Henry	The basic unit of inductance.
Hertz (Hz)	Unit of frequency. One hertz is equal to one cycle per second.
High Fidelity (Hi Fi)	Sound reproduction equipment that reproduces sound as near to the original sound as possible.
High-Pass Filter	A tuned circuit designed to pass all frequencies above a desnigated cut-off frequency. Frequencies below the cut-off frequency are rejected or attenuated.
High Tension	Lethal voltage in the kilovolt range and above.
Hole	A gap left in the covalent bond when a valence electron gains sufficient energy to jump to the conduction band.
Hologram	Three-dimensional picture created with a laser.
Holography	The science dealing with three-dimensional optical recording.
Horizontally Polarized Wave	Electromagnetic wave that has the electric field in the horizontal plane.
Hybrid Circuit	Circuit that combines two technologies (passive and active or discrete and integrated components) onto one microelectronic circuit. Passive components are usually made by thin film techniques, while active components are made with semiconductor techniques.
Hysteresis	Amount that the magnetization of a meterial lags the magnetizing force due to molecular friction. In Schmitt trigger circuits, the difference between the upper and lower trigger points.
IC	Abbreviation for "integrated circuit."
IC Voltage Regulator	Three-terminal device used to hold the output voltage of a power supply constant over a wide range of load variations.
IGFET	Insulated gate field effect transistor. Another name for a "MOSFET."
Impedance	(Z) Measured in ohms it is the total opposition to the flow of current offered by a circuit. Impedance consists of the vector sum of resistance and reactance.
Impedance Coupling	Coupling of two signal amplifier circuits through the use of an impedance such as a inductor.
Impedance Matching	Matching the output impedance of a source to the input impedance of a load to attain maximum power transfer.
Incandescence	State of a material when heated to the point where it emits light (red hot or white hot).
Induced Voltage	Voltage generated in a conductor when subjected to a moving magnetic field.
Inductance	Property of a circuit to oppose a change in current. The moving magnetic field produced by a change in current causes an induced voltage to oppose the original change.
Inductive Circuit	Circuit having greater inductive reactance than capacitive reactance.
Inductive Reactance	Opposition to the flow of AC current produced by an inductor. Measured in Ohms and varies in direct proportion to frequency.
Inductor	Length of conductor used to introduce inductance into a circuit. The conductor is usually wound into a coil to concentrate the magnetic lines of force and maximize the inductance. While any conductor has inductance, in common usage the term inductor usually refers to a coil.
Infrared	Electromagnetic heat radiation whose frequencies are above the microwave frequency band and below red in the visible band.
Inhibit	To stop an action or block data from passing.
In Phase	When two or more waves of the same frequency have their positive and negative peaks occuring at the same time.
Input Impedance	Opposition to the flow of signal current at the input of a circuit or load.
Insulated	When a nonconducting material is used to isolate conducting materials from one another.
Insulating Material	Material that will prevent the flow of current due to its chemical composition.
Insulation Resistance	Resistance of insulating material. The greater the insulation resistance, the better the insulation.
Integrated	When two or more components are combined into a circuit and then incorporated into a single package.
Integrator	A device that approximates and whose output is proportional to an integral of the input signal. A low pass filter.
Intermediate Frequency Amplifier	In a superheterodyne radio it amplifies a fixed frequency lower than the received radio frequency and higher than the audio frequency.
Intermittent	A fault occuring at random intervals of time. Intermittent problems are often difficult to locate because of the random nature. They often don't occur when the technician is present.
Internal Resistance	Every source has some resistance in series with the output current. When current is drawn from the source some power is lost due to the voltage drop across the internal resistance. Usually called output impedance or output resistance.
Intrinsic Material	A semiconductor material with electrical properties essentially characteristic of ideal pure crystal. Essentially silicon or germanium crystal with no measurable impurities.
Intrinsic Stand-Off Ratio	A unijunction transistor (UJT) rating used to determine the firing potential of the device.
Inverting Amplifier	An amplifier that has a 180° phase shift from input to output.
Inverting Input	In an operational amplifier (op-amp) the input that is marked with a minus sign. A signal applied at the inverting input will be given 180° phase shift between input and output.
Ion	An atom with fewer electrons in orbit than the number of protons in the nucleus is a positive ion. An atom with a greater number of electrons in orbit than the number of protons in the nucleus is a negative ion.
Ionized	Atoms become ionized when they gain or lose a valence electron.
j	A prefix used to indicate an imaginary number (operator j).
Jack	Socket or connector into which a plug may be inserted.
JFET	Abbreviation for "junction field effect transistor."
Joule	The unit of work and energy.
Junction	Contact or connection between two or more wires or cables. The area where the P-type material and N-type material meet in a semiconductor.
Junction Diode	A semiconductor diode in which the rectifying characteristics occur at a junction between the n-type and p-type semiconductor materials.
Kilo	Metric prefix for 1000 (10³).
Kilovolt-Ampere	1000 volts at 1 ampere.
Kilowatt-Hour	1000 watts for 1 hour.
Kilowatt-Hour Meter	A meter used by electric utility companies to measure the amount of electric power used by a customer.
Kinetic Energy	Energy associated with motion.
Kirchoff's Current Law	The sum of the currents flowing into a point in a circuit is equal to the sum of the currents flowing out of that same point.
Kirchoff's Voltage Law	The algebraic sum of the voltage drops in a closed path circuit is equal to the algebraic sum of the source voltages applied.
Knee Voltage	The voltage at which a curve joins two relatively straight portions of a characteristic curve. For a PN junction diode, the point in the forward operating region of the characteristic curve where conduction starts to increase rapidly. For a zener diode, the term is often used in reference to the zener voltage rating.
Lag	Difference in time between two waveforms of the same frequency expressed in degrees. Example: One waveform lags another waveform by a certain number of degrees.
Laminated Core	Core made up of sheets of magnetic material insulated from one another by an oxide or varnish.
Lamp	Device that produces light.
Laser	Device that produces a very narrow intense beam of light. The name is an axcronym for "light amplification by stimulated emission of radiation."
Lead	The angle by which one alternating signal leads another in time. Opposite of lag. Also a wire that connects two points in a circuit.
Lead-Acid Cell	Cell made up of lead plates immersed in a sulphuric acid electrolyte. An automobile battery usually consists of six lead-acid cells.
Leakage	Small undesireable flow of current through an insulator or dielectric.
LED	Abbreviation for "light emitting diode."
Left-Hand-Rule	If fingers of the left hand are placed around a wire so that the thumb points in the direction of electron flow, the fingers will be pointing in the direction of the magnetic field being produced by the conductor.
Lenz's Law	The current induced in a circuit due to a change in the magnetic field is so directed as to oppose the flux, or to exert a mechanical force to oppose the motion.
Level Detector	An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs. A comparitor.
Lie Detector	Piece of electronic equipment also called a polygraph used to determine whether a person is telling the truth by looking for dramatic changes in blood pressure, body temperature, breathing rate, heart rate and skin moisture in response to questions.
Light	Electromagnetic radiation in a band of frequencies that can be received by the human eye.
Lifetime	The time from the creation of an electron hole pair until recombination occurs.
Light-Emitting Diode	A semiconductor diode that converts electric energy into electromagnetic radiation at a visible and near infrared frequencies when its pn junction is forward biased.
Limiter	Circuit or device that prevents some portion of its input from reaching the output. A clipper.
Linear	Relationship between input and output in which the output varies in direct proportion to the input.
Linear Scale	A scale in which the divisions are uniformly spaced.
Line Regulation	The ability of a voltage regulator to maintain a constant voltage when the regulator input voltage varies.
Live	Term used to describe a circuit or piece of equipment that is on and has current flow within it.
Load	A source drives a load. Whatever component or piece of equipment is connected to a source and draws current from a source is a load on that source.
Load Current	Current drawn from a source by a load.
Load Impedance	Vector sum of reactance and resistance in a load.
Loading Effect	Large load impedance will draw a small load current and so loading of the source is small (light load). A small load impedance will draw a large load current from the source (heavy load).
Load Regulation	The ability of a voltage regulator to maintain a constant output voltage under varying load currents.
Load Resistance	Resistance of a load.
Logic	Science of dealing with the principle and applications of gates, relays, and switches.
Loss	Term used to describe a decrease in power.
Low-Pass Filter	A tuned circuit designed to pass all frequencies below a designated cut-off frequency.
Magnet	Body that can be used to attract or repel magnetic materials.
Magnetic Circuit Breaker	Circuit breaker that is tripped or activated by use of an electromagnet.
Magnetic Coil	Spiral of a conductor that is called an electromagnet.
Magnetic Core	Material that exists in the center of the magnetic coil either to physically support the windings (nonmagnetic material) or to concentrate the magnetic flux (magnetic material).
Magnetic Field	Magnetic lines of force travelling from the north pole to the south pole of a magnet.
Magnetic Flux	The magnetic lines of force produced by a magnet.
Magnetic Leakage	The passage of magnetic flux outside the path along which it can do useful work.
Magnetic Poles	Points of a magnet from which magnetic lines of force leave (north pole) and arrive (south pole).
Magnetism	Property of some materials to attract or repel others.
Magnetizing Force	Also called magnetic field strength. It is the magnetomotive force per unit length at any given point in a magnetic circuit.
Magnetomotive Force	Force that produces a magnetic field.
Majority Carriers	The conduction band electrons in an n-type material and the valence band holes in a p-type material. Produced by pentavalent impurities in n-type material and trivalent impurities in p-type material.
Matched Impedance	Condition that occurs when the output impedance of a souce is equal to the input impedance of a load.
Matching	Connection of two components or circuits so that maximum power is transferred between the two.
Maximum Power Transfer	A theorem that states that maximum power will be transferred from source to load when input impedance of the load equals the output impedance of the source.
Maxwell	Unit of magnetic flux. One maxwell equals one magnetic line of force.
Mercury Cell	Primary cell using a mercuric oxide cathode, a zinc anode, and a potassium hydroxide electrolyte.
Metal Film Resistor	A resistor in which a film of metal oxide or alloy is deposited on an insulating substrate.
Metal Oxide Field Effect Transistor (MOSFET)	A field effect transistor in which the insulating layer betwen the gate electrode and the channel is a metal oxide layer.
Metal Oxide Resistor	A metal film resistor in which an oxide of metal (such as tin) is deposited as a film onto the substrate.
Meter	Any electrical or electronic measuring device. In the metric system, it is the unit of length equal to 39.37 inches.
Meter FSD Current	Value of meter current needed to cause the needle to deflect to its maximum position (full-scale deflection).
Meter Resistance	DC resistance of the meter's armature coil.
Mica Capacitor	Capacitor using mica as the dielectric.
Microphone	Electroacoustic transducer that converts sound energy into elecric energy.
Microwave	Band of very short wavelength radio waves within the UHF, SHF, and EHF bands.
Midband Gain	Gain of an amplifier operating within its bandwidth.
Midpoint Bias	An amplifier biased at the center of its DC load line.
Mil	One thousandth of an inch (0.001 in.)
Miller's Theorem	A theorem that allows you to represent a feedback capacitor as equivalent input and output shunt capacitors.
Minority Carriers	The conduction band holes in n-type material and valence band electrons in p-type material. Most minority carriers are produced by temperature rather than by doping with impurities.
Mismatch	Term used to describe a difference between the output impedance of a source and the input impedance of a load. A mismatch prevents the maximum transfer of power from source to load.
Modulation	Process by which an information signal (audio for example) is used to modify some characteristic of a higher frequency wave known as a carrier (radio, for example).
Monostable Multivibrator	A nultivibrator with one stable output state. When triggered, the circuit output will switch to the unstable state for a predetermined period of time and then return to the stable state. A timer.
Molecule	Smallest particle of a compound that still retains its characteristics.
MOSFET	Abbreviation for "metal oxide field effect transistor" (also known as an "insulated gate field effect transistor). A field effect transistor in which the insulating layer betwen the gate electrode and the channel is a metal oxide layer.
Moving Coil Microphone	Microphone that uses a moving coil within a fixed magnetic field. Dynamic microphone.
Moving Coil Pick-Up	Dynamic phonograph pick-up in which the stylus causes a coil to move within a fixed magnetic field.
Moving Coil Loudspeaker	Loudspeaker that uses a moving "voice coil" placed within a fixed magnetic field. Audio frequency current in the voice coil causes movement which is mechanically transferred to the speaker cone. Also known as a dynamic loudspeaker.
Multimeter	Electronic test equipment that can perform multiple tasks. Typically one capable of measuring voltage, current, and resistance. More sophisticated modern digital multimeters also measure capacitance, inductance, current gain of transistors, and/or anything else that can be measured electronically.
Multiplier Resistor	Resistor connected in series with a moving coil meter movement to extend the voltage ranges.
Multisegment Display	Device made of several light emitting diodes arranged in a numeric or alphanumeric pattern. By lighting selected segments numeric or alphabet characters can be displayed.
Multivibrator	A class of circuits designed to produce square waves or pulses. Astable multivibrators produce continous pulses without an external stimulus or trigger. Monostable multivibrators produce a single pulse for some predetermind period of time only when triggered. Bistable multivibrators produce a DC output that is stable in either one of two states, either high or low. An external stimulus or trigger is required for the bistable circuit to change states, either high to low or low to high.
Mutual Inductance	Ability of one inductor's lines of force to link with another inductor.
N-Type Semiconductor	A semiconductor compound formed by doping an intrinsic semiconductor with a pentavalent element. An N-type material contains an excess of conduction band electrons.
Negative	Terminal that has an excess of electrons.
Negative Charge	A charge that has more electrons than protons.
Negative Feedback	A feedback signal 180° out of phase with an amplifier input signal. Used to increase amplifier stability, bandwidth, and input impedance. Also reduces distortion.
Negative Ground	A system where the negative terminal of the source is connected to the system's metal chassis.
Negative Ion	An atom having a greater number of electrons in orbit than there are protons in the nucleus.
Negative Resistance	A resistance such that when the current through it increases the voltage drop across the resistance decreases.
Negative Temperature Coefficient	A term used to describe a component whose resistance or capacitance decreases when temperature increases.
Neon Bulb	Glass envelope filled with neon gas which when ionized by an applied voltage will glow red.
Network	Combination of interconnected components, circuits, or systems.
Neutral	A terminal, point, or object with balanced charges. Neither positive nor negative.
Neutral Atom	An atom in which the number of negative charges (electrons in orbit) is equal to the number of positive charges (protons in the nucleus).
Neutral Wire	The conductor of a polyphase circuit or a single-phase, three-wire circuit that is intended to have a ground potential. The potential difference between the neutral and each of the other conductors are approximately equal in magnitude and equally spaced in phase.
Neutron	Subatomic particle in the nucleus of an atom and having no electrical charge.
Nickel-Cadmium Cell	A secondary cell that uses a nickel oxide positive electrode and a cadmium negative electrode.
Node	Junction or branch point in a circuit.
Noise	Unwanted electromagnetic radiation within an electrical or mechanical system.
Non-Inverting Input	An operational amplifier circuit having no phase inversion between the input and output. The terminal on an operational amplifier that is identified by a plus sign.
Non-Linear Scale	A scale in which the divisions are not equally spaced.
Normally Closed	Designation that states that the contacts of a switch or relay are closed or connected when at rest. When activated, the contacts open or separated.
Normally Open	Designation that states that the contacts of a switch or relay are normally open or not connected. When activated the contacts close or become connected.
North Pole	Pole of a magnet out of which magnetic lines of force are assumed to originate.
Norton's Theorem	Any network of voltage sources and resistors can be replaced by a single current source in parallel with a single resistor.
Notch Filter	A filter that blocks a narrow band of frequencies and passes all frequencies above and below the band.
NPN Transistor	A bipolar junction transistor in which a p-type base element is sandwiched between an n-type emitter and an n-type collector.
Nucleus	Core of an atom. The nucleus contains both positive (protons) and neutral (neutrons) subatomic particles.
Octave	Interval between two sounds whose fundamental frequencies differ by a ratio of 2 to 1. 440 Hz. is one octave above 220 Hz.
Offset Null	An op-amp control pin used to eliminate the effects of internal component voltages on the output of the device.
OHM	Unit of resistance symbolized by the Greek capital letter omega ().
Ohmmeter	Device used to measure electrical resistance.
Ohm's Law	Relationship among voltage, current, and resistance. Ohm's law states that current in a resistance varies in direct proportion to voltage applied and inversely proportional to resistance.
Ohms Per Volt	Refers to a value of ohms per volt of full scale defection for a moving coil meter movement. The number of ohms per volt is the reciprocal of the amount of current required to produce full scale deflection of the needle. A meter requiring 50 microamps for full-scale deflection has an internal resistance of 20 k per volt. The higher the ohms per volt rating, the more sensitive the meter.
One-Shot	Monostable multivibrator.
Op-Amp	Abbreviation for operational amplifier.
Open Loop Gain	Gain of an amplifier when no feedback is present.
Open Loop Mode	An amplifier circuit having no means of comparing the output with the input (no feedback).
Operational Amplifier	A high-gain DC amplifier that has a high input impedance and a low output impedance. Op-amps are the most basic type of linear integrated circuits.
Oscillate	To produce a continuous output waveform without an input signal present.
Oscillator	An electronic circuit that produces a continuous output waveform with only DC applied.
Oscilloscope	An instrument used to display a signal graphically. Shows signal amplitude, period, and waveshape in addition to any DC voltage present. A multiple trace oscilloscope can show two or more waveforms at the same time for phase comparison and timing measurements.
Out of Phase	When the maximum and minimum points of two or more waveshapes do not occur at the same time.
Output	Terminal at which a component, circuit, or piece of equipment delivers current, voltage, or power.
Output Impedance	Impedance measured across the output terminals of a device without a load connected.
Output Power	Amount of power a component, circuit, or system can deliver to a load.
Overload	Codition that occurs when the load is greater than the system was designed to handle (load resistance too small, load current too high). Overload results in waveform distortion and/or overheating.
Overload Protection	Protective device such as a fuse or circuit breaker that outomatically disconnects a load when current exceeds a predetermined value.
Paper Capacitor	Fixed capacitor using oiled or waxed paper as a dielectric.
Parallel	Circuit having two or more paths for current flow. Also called shunt.
Parallel Resonant Circuit	Circuit having an inductor and a capacitor in parallel with one another. Circuit offers a high impedance at resonant frequency. Sometimes called a "tank circuit."
Pass Band	The range of frequencies that will be passed and amplified by a tuned amplifier. Also the range of frequencies passed by a band-pass filter.
Passive Component	Component that does not amplify a signal. Resistors and capacitors are examples.
Passive Filter	A filter that contains only passive or nonamplifying components.
Passive System	System that emits no energy. It only receives. It does not transmit or reveal its position.
Peak	Maximum or highest amplitude level.
Peak Inverse Voltage (PIV)	The maximum rated value of a AC voltage acting in the direction opposite to that in which a device is designed to pass current.
Peak to Peak	Difference between the maximum positive and maximum negative values of an AC waveform.
Pentavalent Element	Element whose atoms have five valence electrons. Used in doping intrinsic silicon or germanium to produce n-type semiconductor material. Most commonly used pentavalent materials are arsenic and phosphorus.
Percent of Regulation	The change in output voltage that occurs between no-load and full-load in a DC voltage source. Dividing this change by the full-load value and multiplying the result by 100 gives percent regulation.
Percent of Ripple	The ratio of the effective rms value of ripple voltage to the average value of the total voltage. Expressed as a percentage.
Period	Time to complete one full cycle of a periodic or repeating waveform.
Permanence	Magnetic equivalent of magnetic inductance and consequently equal to the reciprocal of reluctance, just as conductance is equal to the reciprocal of resistance.
Permanent Magnet	Magnet normally made of hardened steel that retains its magnetism indefinately.
Permeability	Measure of how much better a material is as a path for magnetic lines of force with respect to air which has a permeability of one. Symbolized by the Greek lowercase letter mu (μ).
Phase	Angular relationship between two waves.
Phase Angle	Phase difference between two or more waves, normally expressed in degrees.
Phase Shift	Change in phase of a wave form between two points, expressed as degrees of lead or lag.
Phase Shift Oscillator	An oscilator that uses three RC networks in its feedback path to produce the 180° phase shift required for oscillation.
Phase Splitter	Circuit that takes a single input signal and produces two output signals that are 180° apart in phase.
Phonograph	Piece of equipment used to reproduce sound stored on a disk called a phonograph record.
Phosphor	Luminescent material applied to the inner face of a cathode ray tube that when bombarded with electrons will emit light of various colors.
Photoconductive Cell	Material whose resistance decreases or conductance increases when exposed to light.
Photoconduction	A process by which the conductance of a material is change by incident electromagnetic radiation in the visible light spectrum.
Photodetector	Component used to detect or sense light.
Photodiode	A semiconductor diode that changes its electrical characteristics in response to illumination.
Photometer	Meter used to measure light intensity.
Photon	Discrete portion of electromagnetic energy. A small packet of light.
Photoresistor	Also known as a photoconductive cell or light-dependent resistor (LDR). A device whose resistance decreases with exposure to light.
Photovoltaic Cell	Component commonly called a solar cell used to convert light energy into electrical energy.
Pi	Value representin the ratio between the circumference and diameter of a circle and equal to approximately 3.142. Symbolized by the Greek lowercase letter p.
Pierce Oscillator	A variation of the colpitts oscillator. This oscillator uses a quartz crystal in place of the inductor found in the colpitts oscillator feedback network. The crystal maintains a highly stable output frequency.
Piezoelectric Crystal	Crystal material that will generate a voltage when mechanical pressure is applied and conversly will undergo mechanical stress when subjected to a voltage.
Piezoelectric Effect	The production of a voltage between opposite sides of a piezoelectric crystal as a result of pressure or twisting. Also the reverse effect which the application of a voltage to opposite sides causes a deformation to occur at the frequency of the applied voltage. (Converts mechanical energy into electrical energy and electrical energy into mechanical energy.)
Pinch-Off Region	A region on the characteristic curve of an FET in which the gate bias causes the depletion region to extend completely across the channel.
Plastic Film Capacitor	Capacitor in which alternate layers of aluminum foil are separated by thin films of plastic dielectric.
Plate	Conductive electrode in either a capacitor or battery. In vacuum tube technology, it is the name given to the anode.
Plug	Movable connector that is normally connected into a socket or jack.
PNP Transistor	A bipolar junction transistor with an n-type base and p-type emitter and collector.
Pole	In an active filter, a single RC circuit. A one pole filter has one capacitor and one resistor. A two pole filter has two RC circuits and so on.
Polar Coordinates	Either of two numbers that locate a point in a plane by its distance from a fixed point and the angle this line makes with a fixed line.
Polarity	Term used to describe positive and negative charges.
Polarized	A component that must be connected in correct polarity to function and/or prevent destruction. Example: Electrolytic capacitor.
Positive	Polarity of point that attracts electrons as opposed to negative that supplies electrons.
Positive Charge	A charge that exists in a body that has fewer electrons than protons.
Positive Feedback	A feedback signal that is in phase with an amplifier input signal. Positive feedback is necessary for oscillation to occur.
Positive Ground	A system whereby the positive terminal of the source is connected to the system's conducting chassis.
Positive Ion	Atom that has lost one or more valence electrons resulting in a net positive charge.
Potential Difference	Voltage difference between two points which will cause current to flow in a closed circuit.
Potential Energy	Energy that has potential to do work because of its position relative to others.
Potentiometer	A variable resistor with three terminals. Mechanical turning of a shaft can be used to produce variable resistance and potential. Example: A volume control is usually a potentiometer.
Power	Amount of energy converted by a circuit or component in a unit of time, normally seconds. Measured in units of watts (joules/second).
Power Amplifier	An amplifier designed to deliver maximum power output to a load. Example: In an audio system, it is the power amplifier that drives the loudspeaker.
Power Derating Factor	A transistor rating that tells how much the maximum allowable value of P_D decreased for each 1°C rise in ambient temperature.
Power Dissipation	Amount of heat energy generated by a device in 1 second when current flows through it.
Power Factor	Ratio of actual power to apparent power.
Power Loss	Ratio of power absorbed to power delivered.
Power Supply	Electrical equipment used to deliver either AC or DC voltage.
Power Supply Rejection Ratio	A measure of an op-amp's ability to maintain a constant output when the supply voltage varies.
Primary	First winding of a transformer. Winding that is connected to the source as opposed to secondary, which is a winding connected to a load.
Primary Cell	Cell that produces electrical energy through an internal electrochemical action. Once discharged a primary cell cannot be reused.
Printed Circuit Board	Insulating board containing conductive tracks for circuit connections.
Programmable UJT	Unijunction transistor with a variable intrinsic stand-off ratio.
Propagation	Traveling of electromagnetic, electrical, or sound waves through a medium.
Propagation Delay	Time required for a signal to pass through a device or circuit.
Propagation Time	Time required for a wave to travel between two points.
Protoboard	Board with provision for attatching components without solder. Also called a breadboard. Primarily used for constructing experimental circuits.
Proton	Sub atomic particle within the nucleus of an atom. Has a positive charge.
Pulse	Rise and fall of some quantity (usually voltage) for a period of time.
Pulse Fall Time	Time for a pulse to decrease from 90% of its peak value to 10% of its peak value.
Pulse Repetition Frequency	The number of times per second that a pulse is transmitted. Pulse rate.
Pulse Repetition Time	Time interval between the start of two consecutive pulses.
Pulse Rise Time	Time required for a pulse to increase from 10% of its peak value to 90% of its peak value.
Pulse Width	Time interval between the leading edge and trailing edge of a pulse at a point where the amplitude is 50% of the peak value.
Push-Pull Amplifier	Amplifier using two active devices operating 180° apart.
Pythagorean Theorem	A theorem in geometry: The square of the hypotenuse of a right triangle equals the sum of the squares of the other two sides. In electronics used for vector analysis of AC circuits.
Q	Quality factor of an inductor or capacitor. It is the ratio of a component's reactance (energy stored) to its effective series resistance (energy dissipated). For a tuned circuit, a figure of merrit used in bandwidth calculations. Q is the ratio of reactive power to resistive power in a tuned circuit. Also the symbol for charge in coulombs (Q for quantity).
Quiescent	At rest. For an amplifier the term is used to describe a condition with no active input signal.
Quiescent Point	(Q point) A point on the DC load line of a given amplifier that represents the quiescent (no signal) value of output voltage and current for the circuit.
Radar	Acronym for "radio detection and ranging." A system that measures the distance and direction of objects.
Radioastronomy	Branch of astronomy that studies the radio waves generated by celestial bodies and uses these emissions to obtain information about them.
Radio Broadcast	Transmission of music, voice, and other information on radio carrier waves that can be received by the general public.
Radiocommunication	Term used to describe the transfer of information between two or more points by use of radio or electromagnetic waves.
Radio-Frequency Amplifier	Amplifier having one or more active devices to amplify radio signals.
Radio-Frequency Generator	Generator capable of supplying RF energy at any desired frequency in the radio-frequency spectrum.
Radio-Frequency Probe	Probe used in conjunction with an AC meter to measure radio-frequency signals.
RC	Abbreviation for "resistance capacitance," also abbreviation for "radio controled" as in "RC model airplanes."
RC Time Constant	Product of resistance and capacitance in seconds.
Reactance	Symbol "X." Opposition to current flow without the dissipation of energy. Example: The opposition provided by inductance or capacitance to AC current.
Reactive Power	Also called imaginary power or wattless power. It is the power value in "volt amps" obtained from the product of source voltage and source current in a reactive circuit.
Real Number	Number having no imaginary part.
Receiver	Unit or piece of equipment used to receive information.
Recombination	Process by which a conduction band electron gives up energy (in the form of heat or light) and falls into a valence band hole.
Rectangular Coordinates	A Cartesian coordinate of a Cartesion coordinate system whose straight-line axes or coordinate planes are perpendicular.
Rectangular Wave	Also known as a pulse wave. A repeating wave that only operates between two levels or values and remains at one of these values for a small amount of time relative to the other value.
Rectification	Process that converts alternating current to direct current.
Rectifier	Diode circuit that converts alternating current into pulsating direct current.
Reed Relay	Relay consisting of two thin magnetic strips within a glass envelope. When a coil around the envelope is energized, the relay's contacts snap together, making a connection between leads attached to the reed strips.
Regenerative Feedback	Positive feedback. Feedback from the output of an amplifier to the input such that the feedback signal is in phase with the input signal. Used to produce oscillation.
Regulated Power Supply	Power supply that maintains a constant output voltage under changing load conditions.
Regulator	Device or circuit that maintains a desired output under changing conditions.
Relay	Electromechanical device that opens or closes contacts when a current is passed through a coil.
Relative	Not independent. Compared with or with respect to some other measured quantity.
Relaxation Oscillator	Free running circuit that outputs pulses with a period dependent or one or more RC time constants.
Reluctance	Resistance to the flow of magnetic lines of force.
Remanence	Amount a material remains magnetized after the magnetizing force has been removed.
Residual Magnetism	Magnetism remaining in the core of an electromagnet after the coil current is removed.
Resistance	Symbolized "R" and measured in ohms. Opposition to current flow and dissipation of energy in the form of heat.
Resistive Power	Amount of power dissipated as heat in a circuit containing resistive and reactive components. True power as opposed to reactive power.
Resistive Temperature Detector (RTD)	Temperature detector consisting of a fine coil of conducting wire (such as platinum) that will produce a relatively linear increase in resistance as temperature increases.
Resistivity	Measure of a material's resistance to current flow.
Resistor	Component made of material that opposes flow of current and therefore has some value of resistance.
Resistor Color Code	Coding system of colored stripes on a resistor to indicate the resistor's value and tolerance.
Resonance	Circuit condition that occurs at the frequency where inductive reactance (X_L) equals capacitive reactance (X_C).
Reverse Bias	Bias on a PN junction that allows only leakage current (minority carriers) to flow. Positive polarity on the n-type material and negative polarity to the p-type material.
Reverse Breakdown Voltage	Amount of reverse bias that will cause a PN junction to break down and conduct in the reverse direction.
Reverse Current	Current through a diode when reverse biased. An extremely small current also referred to as leakage.
Reverse Saturation Current	Reverse current through a diode caused by thermal activity. This current is not affected by the amount of reverse bias on the component, but does vary with temperature.
RF	Abbreviation for "radio frequency."
Rheostat	Two terminal variable resistor used to control current.
Right Angle Triangle	Triangle having a 90° or square corner.
Ripple Frequency	Frequency of the ripple present in the output of a DC source.
Ripple Voltage	The small variations in Dc voltage that remain after filtering in a power supply.
Rise Time	Time for the leading edge of a pulse to rise from 10% of its peak value to 90% of its peak value.
RL Differentiator	An RL circuit whose output voltage is proportional to the rate of change of the input voltage.
RL Filter	Selective circuit of resistors and inductors that offers little or no opposition to certain frequencies while blocking or attenuating other frequencies.
RL Integrator	RL circuit with an output proportionate to the integral of the input signal.
RMS	Abbreviation for "root mean square."
RMS Value	The rms value of an AC sine wave is 0.707 times the peak value. This is the effective value of an AC sine wave. The rms value of a sine wave is the value of a DC voltage that would produce the same amount of heat in a heating element.
Roll-Off Rate	Rate of change in gain when an amplifier is operated outside of its bandwidth.
Rotary Switch	Electromechanical device that has a rotating shaft connected to one terminal capable of making or breaking a connection to one or more other terminals.
R-2R Ladder	Network or circuit composed of a sequence of L networks connected in tandem. Circuit used in digital to analog converters.
Saturation	Condition in which a further increase in one variable produces no further increase in the resultant effect. In a bipolar junction transistor, the condition when the emitter to collector voltage is less than the emitter to base voltage. This condition puts forward bias on the base to collector junction.
Sawtooth Wave	Repeating waveform that rises from zero to maximum value linearly drops back to zero and repeats. A ramp waveform.
Scale	Set of markings used for measurement.
Schematic Diagram	Illustration of an electrical or electronic circuit with the components represented by their symbols.
Schmitt Trigger	Circuit to convert a given waveform to a square wave output.
Schottky Diode	High-speed diode that has very little junction capacitance. Also known as a "hot-carrier diode" or a "surface-barrier diode."
Scientific Notation	Numbers entered as a number from one to ten multiplied by a power of 10. Example: 8765 = 8.765 x 10³.
Secondary	Output winding of a transformer. Winding that is connected to a load.
Secondary Cell	Electrolytic cell used to store electricity. Once discharged may be restored by recharging by putting current through the cell in the direction opposite to that of discharge current.
Selectivity	Characteristic of a circuit to discriminate between wanted and unwanted signals.
Self-Biasing	Gate bias for a field effect transistor in which source current through a resistor produces the voltage for gate to source bias.
Self-Inductance	Property that causes a counterelectromotive force to be produced in a conductor when the magnetic field expands or collapses with a change of current.
Semiconductor	An element that is neither a good conductor nor a good insulator, but rather lies somewhere between the two. Characterized by a valence shell containing four electrons. Silicon, germanium, and carbon are the semiconductors most frequently used in electronics.
Series Circuit	Circuit in which the components are connected end to end so that current has only one path to follow through the circuit.
Series pParallel Network	Network that contains components connected in both series and parallel.
Series Resonance	Condition that occurs in a series LC circuit at the frequency where inductive reactance equals capacitive reactance. Impedance is minimum; current is maximum limited only by resistance in the circuit.
Seven Segment Display	Device made of several light emitting diodes arranged in a numeric or alphanumeric pattern. By lighting selected segments numeric or alphabet characters can be displayed.
Shells or Bands	Orbital path containing a group of electrons having a common energy level.
Shield	Metal grounded cover used to protect a wire, component, or piece of equipment from stray magnetic and/or electric fields.
Short Circuit	Also called a short. Low resistance conection between two points in a circuit typically causing excessive current.
Shunt Resistor	Resistor connected in parallel or in shunt with another component or circuit.
Signal	Electrical quantity that conveys information.
Signal to Noise Ratio	Ratio of the magnitude of the signal to the magnitude of noise usually expressed in decibels.
Silicon (Si)	Nonmetalic element (atomic number 14) used in pure form as a semiconductor.
Silicon-Controlled Rectifier (SCR)	Three terminal active device that acts as a gated diode. The gate terminal is used to turn the device on allowing current to pass from cathode to anode.
Silicon Controlled Switch	An SCR with an added terminal called an anode gate. A positive pulse either at the anode gate or the cathode gate will turn the device on.
Silicon Dioxide	Glasslike material used as the gate insulating material in a MOSFET.
Silicon Transistor	A bipolar junction transistor using silicon as the semiconducting material.
Silver (Ag)	Precious metal that does not easily corrode and is more conductive than copper.
Silver Mica Capacitor	Mica capacitor with silver deposited directly onto the mica sheets instead of using conductive metal foil.
Silver Solder	Solder composed of silver, copper, and zinc. Has a melting point lower than pure silver but higher than lead-tin solder.
Simplex	Communication in only one direction at a time. Example: FAX.
Simulcast	Broadcasting a program simultaneously in two different forms; for example, a program broadcast in both AM and FM.
Sine	Sine of an angle of a right angle triangle is equal to the opposite side divided by the hypotenuse.
Sine Wave	Wave whose amplitude is the sine of a linear function of time. It is plotted on a graph that plots amplitude against time or radial degrees relative to the angular rotation of an alternator.
Single In-Line Package	Package containing several electronic components (generally resistors) with a single row of connecting pins.
Single Pole Double Throw (SPDT)	Three-terminal switch in which one terminal can be connected to either one of the other terminals.
Single Pole Single Throw (SPST)	Two-terminal switch or relay thet can open or close one circuit.
Single Sideband (SSB)	AM radio communication technique in which the transmitter suppresses one sideband and therefore transmits only a single sideband.
Single Throw Switch	Switch containing only one set of contacts that can be either opened or closed.
Sink	Device such as a load that consumes power or conducts away heat.
Sintering	Process of bonding either a metal or powder by cold pressing it into a desired shape and then heating to form a strong cohesive body.
Sinusoidal	Varying in proportion to the sine of an angle or time function. AC voltage in which the instantaneous value is equal to the sine of the phase angle times the peak value.
SIP	Abbreviation for "single in-line package."
Skin Effect	Tendency of high-frequency (RF) currents to flow near the surface layer of a conductor.
Slew Rate	The maximum rate at which the output voltage of an op-amp can change.
Slide Switch	Switch having a sliding button, bar, or knob.
Slow-Acting Relay	Slow-operating relay that when energized may not pull up the armature for several seconds.
Slow-Blow Fuse	Fuse that can withstand a heavy current (up to ten times its rated value) for a small period of time before it opens.
Snap Switch	Switch containing a spring under tension or compression that causes the contacts to come together suddenly when activated.
SNR	Abbreviation for "signal to noise ratio."
Soft Magnetic Material	Ferromagnetic material that is easily demagnetized.
Software	Program of instructions that directs the operation of a computer.
Solar Cell	Photovoltaic cell that converts light into electric energy. Especially useful as a power source for space vehicles.
Solder	Metallic alloy used to join two metal surfaces.
Soldering	Process of joining two metallic surfaces to make an electrical contact by melting solder (usually tin and lead) across them.
Soldering Iron	Tool with an internal heating element used to heat surfaces being soldered to the point where the solder becomes molten.
Solenoid	An air core coil. Equipped with a movable iron core the solenoid will produce motion. As a result of current through the coil the iron core is pulled into the center of the winding. When the coil is deenergized, a spring pulls the movable core away from the center of the winding. Mechanical devices connected to the movable core are made to move as a result of current through the coil. Example: Electric door locks on some automobiles.
Solid Conductor	Conductor having a single solid wire instead of strands of fine wire twisted together.
Solid State	Pertaining to circuits where signals pass through solid semiconductor material such as transistors and diodes as opposed to vacuum tubes where signals pass through a vacuum.
Sonar	Acronym for "sound navigation and ranging." A system using reflected sound waves to determine the position of some target.
Sonic	Pertaining to sound.
Sound Wave	Pressure waves propagated through air or other plastic media. Sound waves are generally audible to the human ear if the frequency is between approximately 20 and 20,000 vibrations per second (hertz).
Source	Device that provides signal power or energy to a load.
Source Follower	FET amplifier in which signal is applied between gate and drain with output taken between source and drain. Also called "common drain."
Source Impedance	Impedance through which output current is taken from a source.
South Pole	Pole of a magnet into which magnetic lines of force are assumed to enter.
Spark	Momentary discharge of electrical energy due to ionization of air or other dielectric material separating two charges.
SPDT	Single pole double throw.
Speaker	Also called "loudspeaker." Transducer that converts electrical energy into mechanical energy at audio frequencies.
Spectrum	Arrangement or display of light or other forms of electromagnetic radiation separated according to wavelength, energy, or some other property.
Spectrum Analyzer	Instrument used to display the frequency domain of a waveform plotting amplitude against frequency.
Speed-Up Capacitor	Capacitor added to the base circuit of a BJT switching circuit to improve the switching time of the device.
SPST	Abbreviation for "single pole single throw."
Square Wave	Wave that alternates between two fixed values for an equal amount of time.
Static	Crackling noise heard on AM radio receivers. Caused by electric storms or electric devices.
Static Electricity	Stationary electric charges.
Static Reverse Current	Reverse current through a zener diode when the reverse voltage across the diode is less than the zener voltage rating of the device.
Stator	Stationary part of some rotary device such as a variable capacitor.
Step-Down Transformer	Transformer in which the output AC voltage is less than the input AC voltage.
Step-Up Transformer	Transformer in which the output AC voltage is greater than the input AC voltage.
Stereo Sound	System in which reproduced sound is delivered through two or more channels to give a sense of direction to the source.
Stop Band	Range of frequencies outside the pass band of a tuned amplifier.
Storage Time	In a BJT switching circuit, it is the time required for collector current to drop from 100% to 90% of its maximum value.
Stranded Conductor	Conductor composed of a group of strands of wire twisted together.
Stray Capacitance	Undesirable capacitance that exists between two conductors such as two leads or one lead and a metal chassis.
Subassembly	Components contained in a unit for convenience in assembling or servicing equipment.
Subatomic	Particles such as electrons, protons, and neutrons that are smaller than atoms.
Substrate	Mechanical insulating support upon which a device is fabricated.
Summing Amplifier	An op-amp circuit whose output is proportional to the sum of its instantaneous voltages.
Superconductor	Metal such as lead or niobium that, when cooled to within a few degrees of absolute zero, can conduct current with no resistance.
Superheterodyne Receiver	Radio receiver that converts all radio frequencies to a fixed intermediate frequency to maximize gain and bandwidth before demodulation.
Super High Frequency (SHF)	Frequency band between 3 GHz and 30 GHz. So desiganted by Federal Communications Comission (FCC).
Superposition Theorem	Theorem designed to simplify networks containing two or more sources. It states that in a network containing more than one source, the current at any one point is equal to the algebraic sum of the currents produced by each source acting separately.
Supply Voltage	Voltage provided by a power source.
Surface-Barrier Diode (Schottky diode)	High-speed diode that has very little junction capacitance. Also known as a "hot-carrier diode."
Surface Leakage Current	Diode reverse current that passes along the surface of the semiconductor materials.
Surge Current	High charging current that flows into a power supply filter capacitor as the power is first turned on.
Sweep Generator	Test instrument designed to produce a voltage that continously varies in frequency over a band of frequencies. Used as a souce to display frequency response of a circuit on an oscilloscope.
Switch	Electrical device having two states, on (closed) or off (open). Ideally having zero impedance when closed and infinite impedance when open.
Switching Transistor	transistor designed to change rapidly between saturation and cut-off.
Synchronization	Also called sync. Precise matching of two waves or functions.
Synchronous	Two or more signals in step or in phase.
Sync Pulse	Pulse used as a reference for synchronization.
System	Combination of several pieces of equipment to perform in a particular manner.
Tank Circuit	Parallel resonant circuit containing only a coil and a capacitor. Both the coil and capacitor store electrical energy for part of each cycle.
Tantalum Capacitor	Electrolytic capacitor having a tantalum foil anode. Able to have a large capacity in a small package.
Tap	Electrical connection to some point other than at the ends of a resistor or inductor.
Tapered	Nonunifrom distribution of resistance per unit length throughout the element of a potentiometer.
Technician	Expert in troubleshooting circuit and system malfunctions. Along with a thorough knowledge of test equipment and how to use it to diagnose problems, the technician is also familiar with how to repair or replace faulty components. Technicians basically translate theory into action.
Telegraphy	Communication between two points by sending and receiving a series of current pulses either through wire or by radio.
Telemetry	Transmission of instrument readings to a remote location either by wire or by radio.
Telephone	Apparatus designed to convert sound waves into electrical waves which are sent to and reproduced at a distant point.
Telephone Line	Wires existing between subscribers and central stations in a telephone system.
Telephony	Telecommunications system involving the transmission of speech information, allowing two or more persons to communicate verbally.
Teletypewriter	Electric typewriter that like a teleprinter can produce coded signals corresponding to the keys pressed or print characters corresponding to the coded signals received.
Television	System that converts both audio and visual information into corresponding electrical signals that are then transmitted through wires or by radio waves to a receiver, which reproduces the original information.
Telex	Teletypewriter exchange service.
Temperature Coefficient of Frequency	Rate at which frequency changes with temperature.
Tera (T)	Metric prefixes that represents 10¹².
Terminal	Point at which electrical connections are made.
Tesla (T)	Unit of magnetic flux density (1 tesla = 1 Wb/m²).
Test	Sequence of operations intended to verify the correct operation or malfunctioning of a piece of equipment or system.
Thermal Relay	Relay activated by a heating element.
Thermal Runaway	Problem that can develop in an amplifier when an increase in temperature causes an increase in collector current. The increase in collector current causes a further increase in temperature and so on. Unless the circuit is designed to prevent this condition, the device can be driven into saturation.
Thermal Stability	The ability of a circuit to maintain stable characteristics in spite of increased temperature.
Thermistor	Temperature-sensitive semiconductor that has a negative temperature coefficient of resistance. As temperature increases, resistance decreases.
Thermocouple	Temperature transducer consisting of two dissimilar metals welded together at one end to form a junction that when heated will generate a voltage.
Thermometry	Relating to the measuring of temperature.
Thermostat	Device that opens or closes a circuit in response to changes in temperature.
Thevenin's Theorem	Theorem that replaces any complex network with a single voltage source in series with a single resistance.
Thick Film Capacitor	Capacitor consisting of two thick-film layers of conductive film separated by a deposited thick-layer dielectric film.
Thick Film Resistor	Fixed value resistor consisting of thick-film resistive element made from metal particles and glass powder.
Thin Film Capacitor	Capacitor in which both the electrodes and the dielectric are deposited in layers on a substrate.
Thin Film Detector (TFD)	A temperature detector containing a thin layer of platinum and used for precise temperature readings.
Three-Phase Supply	AC supply that consists of three AC voltages 120° out of phase with each other.
Threshold	Minimum point at which an effect is produced or detected.
Threshold Voltage	For an enhancement MOSFET, the minimum gate source voltage required for conduction of source drain current.
Thyristor	A term used to classify all four-layer semiconductor devices. SCRs and triacs are examples of thyristors.
Time Constant (t)	Time required for a capacitor in an RC circuit to charge to 63% of the remaining potential across the circuit. Also time required for current to reach 63% of maximum value in an RL circuit. Time constant of an RC circuit is the product of R and C. Time constant of an RL circuit is equal to inductance divided by resistance.
Time Division Multiplexing (TDM)	Transmission of two or more signals on the same path, but at differenttimes.
Time Domain Analysis	A method of representing a waveform by plotting amplitude over time.
Toggle Switch	Spring loaded switch that is put in one of two positions either on or off.
Tolerance	Permissible deviation from a specified value normally expressed as a percentage.
TO Package	Cylindrical, metal can type of package of some semiconductor components.
Toroidal Coil	Coil wound on a doughnut shaped core.
Transconductance	Also called mutual conductance. Ratio of a change in output current to the change in input voltage that caused it.
Transducer	Device that converts energy from one form to another.
Transformer	Inductor with two or more windings. Through mutual inductance, current in one winding called a primary will induce current into the other windings called secondaries.
Transformer Coupling	Also called inductive coupling. Coupling of two circuits by means of mutual inductance provided by a transformer.
Transistor	Term derived from "transfer resistor." Semiconductor device that can be used as an amplifier or as an electronic switch.
Transmission	Sending of information.
Transmission Line	Conducting line used to transmit signal energy between two points.
Transmitter	Equipment used to achieve transmission.
Triac	Bidirectional gate controlled thyristor similar to an SCR but capable of conducting in both directions. Provides full-wave control of AC power.
Triangular Wave	A repeating wave that has equal positive going and negative going ramps. The ramps have linear rates of change with time.
Trigger	Pulse used to initiate a circuit action.
Triggering	Initiation of an action in a circuit, which then functions for a predetermined time. Example: The duration of one sweep in a cathode ray tube.
Trimmer	Small value variable capacitor, resistor, or inductor used to fine-tune a larger value.
Trivalent Element	One having three valence electrons. Used as an impurity in semiconductor material to produce p-type material. Most commonly used trivalent elements are aluminum, gallium, and boron.
Troubleshooting	Systematic approach to locating the cause of a fault in an electronic circuit or system.
Tuned Circuit	Circuit that can have its component values adjusted so that it responds to one selected frequency and rejects all others.
Tunnel Diode	Heavily doped junction diode that has negative resistance in the forward direction of its operating range.
Turn-Off Time	Sum of storage time and fall time.
Turn-On Time	Sum of delay time and rise time.
Turns Ratio	Ratio of the number of turns in the secondary winding of a transformer to the number of turns in the primary winding.
Two Phase	Two repeating waveforms having a phase difference of 90°.
UHF	Abbreviation for "ultra high frequency."
Ultrasonic	Signals that are just above the frequency range of human hearing of approximately 20 kHz.
Uncharged	Material having atoms with the same number of electrons in orbit as the number of protons in the nucleus. Having no electrical charge.
Unijunction Transistor	Three terminal device that acts as a diode with its own internal voltage divider biasing circuit.
Unity Gain Frequency	Frequency of operation for a device where the gain of the component drops to unity.
VA	Abbreviation for "volt ampere."
Vacuum Tube	Electron tube evacuated to such a degree that its electrical characteristics are essentially unaffected by the presence of residual gas or vapor. Have been essentially replaced by transistors for amplification and rectification. Cathode ray tubes are still used as display devices.
Valence Shell	The outermost electron shell for a given atom. The number of electrons in this shell determines the conductivity of the atom.
Varactor Diode	PN junction diode with a high junction capacitance when reverse biased. Most often used as a voltage controlled capacitor. The varactor is also called vari-cap, tuning diode, and epi-cap.
Variable Capacitor	Capacitor whose capacitance can be change by varying the effective area of the plates or the distance between the plates.
Variable Resistor	Resistor whose resistance can be changed by turning a shaft. See also Potentiometer and Rheostat.
VCR	Abbreviation for "video cassette recorder."
Vector	Quantity having both magnitude and direction. Normally represented by a line. Length of the line indicates magnitude and orientation indicates direction.
Vector Diagram	Arrangement of vectors showing phase relationships between two or more AC quantities of the same frequency.
Vertical MOS	Enhancement type MOSFET designed to handle much greater values of drain current than standard E-MOSFET.
Very High Frequency (VHF)	Electromagnetic frequency band from 30 MHz to 300 MHz.
Very Low Frequency (VLF)	Frequency band from 3 kHz to 30 kHz.
Video	Relating to any picture or visual information. From the Latin word meaning "I see."
Video Amplifier	Amplifier having one or more stages designed to amplify video signals.
Virtual Ground	Point in a circuit that is always at approximately ground potential. Often a ground for voltage, but not for current.
Voice Coil	Coil attached to the diaphragm of a moving coil loudspeaker. The coil is moved through an air gap between magnetic pole pieces.
Voice Synthesizer	Synthesizer that can simulate speech by stringing together phonemes.
Volt	Unit of potential difference or electromotive force. One volt is the potential difference needed to produce one ampere of current through a resistance of one ohm.
Voltage (V)	Term used to designate electrical pressure or force that causes current to flow.
Voltage Amplifier	Amplifier designed to build up signal voltage. By design amplifiers can have a large voltage gain or a large current gain or a large power gain. Voltage amplifiers are designed to maximize voltage gain often at the expense of current gain or power gain.
Voltage Controlled Oscillator	Oscillator whose output frequency depends on an input control voltage.
Voltage Divider	Fixed or variable series resistor network connected across a voltage to obtain a desired fraction of that voltage.
Voltage Divider Biasing	Biasing method used with amplifiers in which two series resistors connected across a source. The junction of the two biasing resistors provides correct bias voltage for the amplifier.
Voltage Drop	Voltage or difference in potential developed across a component due to current flow.
Voltage Feedback	Feedback configuration where a portion of the output voltage is fed back to the input of an amplifier.
Voltage Follower	Operational amplifier circuit characterized by a high input impedance, low output impedance, and unity voltage gain. Used as a buffer between a source and a low impedance load.
Voltage Gain	Also called voltage amplification. Ratio of amplifier output voltage to input voltage usually expressed in decibels.
Voltage Multiplier	Rectifier circuit using diodes and capacitors to produce a DC output voltage that is some multiple of the peak value of AC input voltage. Cost-effective way of producing higher DC voltages. Voltage doublers and voltage triplers are examples.
Voltage Rating	Maximum voltage a component can withstand without breaking down.
Voltage Regulator	Device or circuit that maintains constant output voltage (within certain limits) in spite of changing line voltage and/or load current.
Voltage Source	Circuit or device that supplies voltage to a load.
Voltaic Cell	Primary cell having two unlike electrodes immersed in a solution that chemically interacts to produce a voltage.
Volt-Ampere	Unit of apparent power in an AC circuit containing capacitive or inductive reactance. Apparent power is the sum of source voltage and current.
Voltmeter	Instrument used to measure difference in potential between two points.
Volume	Magnitude or power level of audio frequency. Measured in volume units (VU).
Watt	Unit of electrical power required to do work at the rate of one joule per second. One watt of power is expended when one ampere of direct current flows through a resistance of one ohm. In an AC circuit, true power is the product of effective volts and effective amperes, multiplied by the power factor.
Wattage Rating	Maximum power a device can safely handle continuously.
Watt-hour	Unit of electrical work, equal to a power of one watt being absorbed for one hour.
Wattmeter	Instrument used to measure electric power in watts.
Wave	Electric, electromagnetic, acoustic, mechanical, or other form whose physical activity rises and falls or advances and retreats periodically as it travels through some medium.
Waveform	Shape of a wave.
Waveguide	Rectangular or circular pipe used to guide electromagnetic waves at micro frequencies.
Wavelength (l)	Distance between two points of corresponding phase and is equal to waveform velocity divided by frequency.
Weber (Wb)	Unit of magnetic flux. One Weber is the amount of flux that when linked with a single turn of wire for an interval of one second will induce an electromotive force of one volt.
Wienbridge Oscillator	Oscillator that uses an RC low-pass filter and an RC high-pass filter to set the frequency of oscillations.
Wet Cell	Secondary cell using a liquid as an electrolyte.
Wetting	Term used in soldering to describe the condition that occurs when the metals are being soldered are hot enough to melt the solder so it flows over the surface.
Wheatstone Bridge	Four-arm bridge circuit used to measure resistance, inductance or capacitance.
Wideband Amplifier	Also called "broadband amplifier." Amplifier with a flat response over a wide range of frequencies.
Winding	One or more turns of a conductor wound in the form of a coil.
Wire	Single solid or stranded group of conductors having a low resistance to current flow. Used to make connections between circuits or points in a circuit.
Wire Gauge	American wire gauge (AWG) is a system of numerical designations of wire diameters.
Wireless	Term describing radio communication that requires no wired between two communicating points.
Wire-Wound Resistor	Resistor in which the resistive element is a length of high-resistance wire or ribbon, usually nichrome, wound onto an insulating form.
Wire Wrapping	Method of making a connection by wrapping wire around a rectangular pin.
Woofer	Large loudspeaker designed primarily to reproduce low-frequency audio signals.
Work	Work is done anytime energy is transformed from one type to another. The amount of work done is dependent on the amount of energy transformed.
X	Symbol for reactance.
x-axis	Horizontal axis.
Y	Symbol for admittance.
y-axis	Vertical axis.
z-axis	Axis perpendicular to both x- and y-axes.
Zener diode	Semiconductor diode in which reverse breakdown voltage current causes the diode to develop a constant voltage. Used as a clamp for voltage regulation.
Zeroing	Calibrating a meter so that it shows a value of zero when zero is being measured.

Last updated on 26/02/2024

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