[sdiy] Temperature Compensated VCO attempt - help?

[patchell]

    Scott, tomorrow morning I should be ready to test a slightly modified
version of your circuit (basically your temp sensor in what I already had).
Got it all wired up and working, but, I don't see so good in artificial
light anymore...so first thing in the morning.  Also have my blue ice
freezing in the freezer...gonna give this thing a wide range of temps.

Scott Bernardi wrote:

> I've made an attempt at an electronically temperature compensated
> exponential generator and VCO. I built it into a thru-zero FM VCO based
> on an Electronotes design. The VCO works, but the exponential generator
> suffers from linearity problems. I can tune it to a nice 1v/octave
> response using my VCO tuner
> (http://home.attbi.com/~sbernardi/elec/og2/vco_tuner.html) at 0v CV, but
> as soon as I deviate from that either higher or lower in frequency, the
> scaling is off.
> I've got a pretty detailed theory of operation and schematic at
> http://home.attbi.com/~sbernardi/elec/og2/tempcomp_vco_theory.htm.
> Jim (Patchell), I was especially interested in your temp compensated
> VCO, and notice you changed the circuit because the previous one was
> "bogus".  I believe on your previous circuit you were using a delta Vbe
> bandgap reference like mine - was that giving you problems? I also
> notice you are using a different configuration for your multiplier OTA
> that "linearizes" it.  I suspect it might be my OTA multiplier that's
> causing the problems.
> Anybody care to comment?

--
 -Jim
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