Fork me on GitHub

Project Notes

#687 Crystal-locked 455kHz Oscillator

Testing a 455kHz crystal-locked Pierce oscillator using CD4001 CMOS NOR gates.



This circuit is a variation on the theme from LEAP#656 Crystal-Locked Schmitt Oscillator using NOR gates and a 4MHz crystal.

Circuit Design

Key design notes:

  • Instead of simple inverters, the design uses NOR gates from a CD4001 chip. The NOR gate may either be wired:
    • both inputs tied together, so the output is always the inverse of the input
    • one input tied to ground, so the output is always the inverse of the other input
  • With a 455kHHz crystal, relatively large stabilization capacitors are required to maintain oscilation (in this case >=300pF). The mis-matched stabilization capacitors help ensure oscillation starts.
  • A feedback resistor is not essential and has been left out as the frequency is relatively low.




Test Results

Measuring 452.3kHz, with scope connections as follows:

  • CH1 Yellow: buffered oscillator output
  • CH2 Blue: oscillator output

At this frequency, the buffered output is a nice square wave.


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

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

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - 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
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.