Spehro Pefhany wrote:
> Sorry, I don't agree, at least prima facie, that some resistance would
> affect the validity of the equations-- I think the effect would be to
> lower the Q somewhat, not to change the resonant frequency directly.

I wasn't talking about changing the resonant frequency, only how to compute
the load presented to the crystal in a given situation.  Think about the
limiting case where the oscillator output had 0 impedence.  In other words,
it's a pure voltage source.  Hanging a capacitor on its output would not
change the waveform on either side of the crystal at all.  By definition,
the voltage source would produce the same voltage regardless of what current
it takes to do that.  In that case, the crystal output capacitor would be
the sole crystal load.  This proves that driver impedence has an effect on
how the load is calculated, at least when the driver impedence is low.


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