Paul Burridge wrote...

Tim Wescott wrote:

The varactor capacitance change is instantaneous -- think of a capacitor
who's plate spacing is dependent on it's voltage. This is why varactors
are used for frequency multiplication -- that capacitance change
"squeezes" the pulse to generate lots of harmonics.

Rubbish. Varactors are not used for freqency mulitplication. They are
freequenty used in VXCOs for modulating (or otherwise varying) the
oscillator output frequency by means of applying a DC bias voltage
which alters the capacitance of the PN junction.

Your own rubbish, Paul. In truth of fact, varactors are nicely used
for frequency multiplication, just as Tim stated. They also work well
for VCO FM modulation, but users must keep in mind their instantaneous
capacitance-change property and be careful to bias them in appropriate
higher-voltage bias regions, or risk unintended distortion. When used
as multipliers, low-voltage bias with large signals enhances the effect.

Thanks,
- Win

whill_at_picovolt-dot-com