more frequency tracking..

[Martin Czech]

> anyone have any thoughts on using a PLL to extract a clean sine from an
> arbitrary signal and then running that across a series RC, tapping off of
> one of the components then running that to a buffer and then rectifying and
> filtering to get a frequency tracking CV?  how large a delay is usually
> introduced in a PLL before the VCO matches the input frequency?  which PLL's
> have the lowest delay?

Someone on the list experimented with a 4046 PLL a year (or more) ago.
It is a wide range PLL and works with square/pulse waves.

With PLLs there is always a run in time, until the control ciruit locks.
If the phase comparator filter is very slow, it gives a kind of 
sproooiijng effect, whereas if the filter is fast (or none at all)
it introduces distortion (PWM) of the vco waveform.

If you are using a pll, the control circuit itself already provides the
necessary frequency dependent voltage, by driving the loop vco. If you
use a linear vco, you get a linear frequency to voltage conversion, in
case of an exponential vco the voltage is logarithmical.

m.c.

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