[sdiy] simple PLL frequency-to-voltage converter?

harrybissell at wowway.com harrybissell at wowway.com
Fri Nov 14 21:05:50 CET 2008

What do you want a FVC to do... ?

How long can you afford to wait for an accurate result ?

How much noise and ripple can you stand ?

What does the input signal look like ?

Most FVC fall into two catagories... Tachometer circuits that need
a large number of cycles to get an accurate result, and period measuring
circuits that take between one half to two cycles to get a result.

IMHO a PLL circuit belongs in the tachometer class...

The Korg MS-20 is an example of a clever tachometer circuit with extended
range and allows a trade-off between speed of response and ripple.

Almost all other circuits  (for example from Korg, Roland, Gentle Electric,
360 Systems Slavedriver, Etherewave PV converter) use the period measurement

BIGGEST trouble is cleaning up an input waveform to the point where it can
give accurate results. In most cases this would mean being able to extract a
clean, jitter free square wave from the input.  This is very hard for real
world audio inputs, especially guitar.

The other problem is determining when to stop tracking an audio input and
start holding a last, valid data.

What do you like ???   :^)

H^) harry

On Thu, 13 Nov 2008 14:39:44 -0500, alfred.pear wrote
> can anyone reccomend a schematic for a simple FVC using only PLLs
> and/or op amps as ICs?
> many of the circuits i've found seem to include dedicated ICs or 
> logic chips..
> -ap
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Harry Bissell & Nora Abdullah 4eva

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