VC envelopes

[chordman at flash.net]

Juergen wrote:
> As far as I see it, the problem with the 3080 is that the offset voltage
> varies with the amplifier bias current, so you can only compensate
> for one point.

Very true, so...

Consider a dual OTA such as the LM13600.  OTA #1 is configured as a normal
VCA.  OTA #2 is gain controlled by the same signal as OTA #1, but it's
input signal is a constant voltage provided by a reference source and a
trimmer.  Now the CV feedthru should appear on both OTAs, so couldn't the
output of OTA #2 simply be applied to OTA #1 at the inverting input?
Would that not cancel most of the CV feedthru?  These parts are rather
inexpensive and the spec claims very close matching between the two OTAs in
a given package.  From that I'd expect the feedthru behaviour to be very
close.

Or do I need yet another dosage increase?

-- Scott