AW: Re: F-V converter and Ring Mod. stuff
HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Fri Feb 23 21:00:00 CET 1996
> Note that, with an exponential VCO, the loop gain increases
> exponentially with frequency. This is a good thing for tracking, as
> the tracking actually gets faster at higher pitches, but you'll get
> more of a spring effect too. I 'spose it would be best if the filter
> could change tuning in parallel with the VCO.
> Some nonlinearities before the VCO could also help.
Just an idea:
The "nonlinearity" could be a logging circuit!
So we'd have: Phase Comparator -> RC-Filter -> Log -> ExpVCO
The PLL loop sees a linear VCO then, and all the well-known PLL
theory would apply. And we could use the Log output for deriving
a V/8ve CV as desired.
Note that the Log circuit could be a very cheap one (without
temperature compensation), because the accuracy is only determined
by the exponential VCO (closed loop).
What do You think?
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