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Project Notes

#242 PierceOscillator

Test a Pierce Oscillator made with a minimum of components.

The Build


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

Power Consumption

Supply Current
5V 2.6mA
9V 4.4mA



The Schematic



Sample Traces

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)
D368L0I 3.6865
D400048I 4.00006
4.000 4.00036
D427K0I 4.2735
D427L0I 4.2735
4.43619 KDSI OE 4.4356
D700L0I 7.0001
CL7.023 7.0231
8.000 8.00043
D10.24L0I 10.2409
12.000 12.0010
D143L0I 14.3197
D159L0T 15.9758
16.000 16.0023
20.000 20.0032

An example trace with 7MHz crystal, 9V supply:


And 16MHz crystal, 9V supply:


Credits and References

About LEAP#242 OscillatorsCrystal
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.