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Project Notes

#230 MinimalLCOscillator

Test an LC oscillator of just 5 components


I borrowed this idea and circuit design from stoneslice’s 1MHz Oscillator video.

I’m not sure how the circuit fits into the taxonomy of oscillator circuits, but it is similar to a Colpitts oscillator circuit - but one capacitor is replaced with a resistor.

I tried a range of component values on a breadboard. To sustain the oscillation, I found I had to increase the value of the resistor - 4.7kΩ proved good for all cases.

L C frequency
470µH 47pF 1.6MHz
150µH 47pF 2.9MHz
470µH 68pF 1.5MHz
150µH 68pF 2.7MHz

The effect of the resistor seems to alter the resonant frequency of the “impure” tank circuit. For example, I’d expect with 150µH/47pF the frequency to be 1.89MHz when in fact I measure 2.819MHz.

Nevertheless, an interesting self-oscillating circuit.

Soldered on a PCB with 150µH/47pF and a J201 n-FET, there are no issues sustaining an oscillation, however the frequency is not particularly stable and there’s a distinct second harmonic.





The Schematic

The Build

Credits and References

About LEAP#230 LCOscillators
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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.