# #230 MinimalLCOscillator

Test an LC oscillator of just 5 components

## Notes

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.

## Construction

## Credits and References

- 1MHz Oscillator - stoneslice
- Colpitts oscillator - wikipedia
- J201 datasheet
- ..as mentioned on my blog