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Pierce oscillator, from crystal to LC

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neazoi

neazoi

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Hello a simple crystal pierce oscillator is shown here
**broken link removed**
Since the crystal is used as a feedback element, I was wondering if it can be replaced by an LC combination in order to make a vfo.
I have not seen any such circuits on the net.
 

There is a family of oscillators which use LC resonance.
These are Colpitts, Clapp, Hartley.

The crystal is not replaced pin-for-pin with an inductor-capacitor pair, if that's what you're looking for. The types mentioned above arrange the LC differently, and have more than one inductor or capacitor.
 

This circuit will work with a wide combination of L and C.
 

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    neazoi

    neazoi

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Yes, this was a design I did in another post. It can easily be altered for use with a JFET.
 

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    neazoi

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E-design said:
Yes, this was a design I did in another post. It can easily be altered for use with a JFET.
Click to expand...

Thank you! I will try it, probably the fet version.
Have you got any clue about it's stability and frequency coverage without any components alterations apart from the LC?
 

The short term stability will be affected by the loaded-Q of the LC combination. High LC ratios will have higher Q and better short term stability.

It can be seen in the plot below by keeping L constant and varying C the loaded-Q increase with higher frequencies.

If you want a VFO oscillator with more constant Q over the frequency range, then look at the Vackar topology.

https://en.wikipedia.org/wiki/Vackář_oscillator
 

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