Test a Pierce Oscillator made with a minimum of components.
The Pierce oscillator is named for its inventor, George W. Pierce (1872-1956). It is a derivative of the Colpitts oscillator, and can be implemented using a minimum of components. Typically: a digital inverter, one resistor, two capacitors, and a quartz crystal.
The circuit I’m testing here is from KF5OBS. It features:
- BJT in place of the digital inverter
- takes advantage of the base-emitter capacitance to eliminate one capacitor
I’ve tested with a range of crystals from 3Mhz to 20MHz, all oscillate satisfatorily. It does not wotk with slower crystals such as 32768Hz.
Here are the measured frequencies for a batch of crystals according to my oscilloscope:
|Marking||Measured Frequency (MHz)|
|4.43619 KDSI OE||4.4356|
An example trace with 7MHz crystal, 9V supply:
And 16MHz crystal, 9V supply: