This is an oscillator that can be stuffed to be either a crystal oscillator (with a 74HC04) or an RC oscillator (with a 74HC14).

I originally designed two boards. One for a crystal oscillator and one for an RC oscillator. So I decided to design one board that could be used either way.

As a crystal oscillator it takes 2MHz - 16 MHz crystals. As an RC oscillator the suggested values are for 1KHz.

Both circuits can operate down to the lower voltage limit of the CMOS gates which is about 1.8V. With the RC oscillator the voltage also changes the frequency so it can be used as a crude VCO. When you do that you are also changing the output voltage so it might have a problem driving other circuitry. Although the values shown for the RC oscillator are for 1KHz, with other values the circuit can oscillate up to several MHz.

To use it as an RC oscillator:

1. U1: Use a 74HC14 instead of the 74HC04.

2. R2: remains 10K.

3. XTAL: Use 10K trimpot (3362P) instead of xtal.

4. C2: Use4700pF instead of 22pF.

5. C3: not loaded.

6. R1: not loaded.

Notes:

1. I left a strip of the ground plane exposed so I can bond it to another board if I need to.

2. I gave it two outputs in case I need them.

3. I recommend you use an IC socket with machine-tooled pins for U1.

4. And so I can try different component values I used the pins from an IC socket with machine-tooled pins for those components.

If you are not already a Maker (and you want to be one) see my tutorial on Making Things at www.jmargolin.com/making/jm_making.htm

JM