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Project Notes

#656 Crystal-Locked Schmitt Oscillator

Testing a basic crystal-locked Schmitt oscillator using a 74HC14.

Build

Notes

I tested the basic SchmittOscillator a very long time ago in LEAP#022. I was prompted to try the crystal-locked variation after seeing CD40106 aka 74C14 covered in IMSAI Guy’s chip of the day:

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Circuit Design

the slowest crystal I have to hand is 4MHz, so I needed to add 20pF stabilization capacitors to maintain oscilation. The second inverter buffers the output and the 51kΩ feedback resistor ensure’s the oscillator is kicked into action.

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schematic

Build

Test Results

4.00019MHz according to my scope:

scope

Credits and References

About LEAP#656 CMOS/TTLOscillators
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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, 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!).

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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.