[sdiy] Temperature Compensated VCO attempt - help?

[Scott Bernardi]

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?