Analog circuit noise is to limit the performance of the main factors. Noise is divided into the following categories:
Conduction (Conducted Emissions) - analog circuits and other circuits connected to the noise generated at. In the analog circuits, this noise can usually be ignored, unless the power circuits (e.g., a large current draw from the power audio amplifier).
Radiated noise (Radiated Emissions) - analog circuit generated or emitted into the air. In the analog circuits, this noise can usually be ignored, except in high-frequency circuits (such as video).
Conduction (Conducted Susceptibility) - the analog circuits and other circuits when in contact conduction from an external circuit to the noise generated when the analog circuit. Analog circuitry must be connected to the outside, at least, the power supply, input and output connections. Noise can utilize the various existing channels of conduction current.
Radiation (Radiated Susceptibility) - It is composed of an external power supply through the air radiation (or conduction to the analog circuitry) received. In many cases, the analog circuit structure resides in high speed digital printed circuit board, including a digital signal processing chip, high-speed synchronous clock pulses and digital signals cause considerable changes in the radio frequency interference (RFI). Also some of the radiated noise source range is quite extensive: Digital system power switch telephone network, radio broadcasting and television, fluorescent lighting, personal computers, thunderstorm lightning and so on. Although the analog circuit is mainly the audio, but the RF interference at the output may have a significant noise.
