[sdiy] PAIA VCO, LM13700 diode temp comp.

[Ian Fritz]

At 05:42 PM 10/17/05, karl dalen wrote:
>Long time ago there was discussions on the PAIA
>VCO temp drift compensation using the diodes of
>the LM13700, how did that turned out?
>
>Was it a good idea of temp compensation?

I built a similar VCO a few months ago, as an aux VCO to use in my chaos 
box.  My main trouble with this circuit involved the V/Oct tracking.  After 
much experimenting and tweaking the best tracking I got was +/- 0.5% from 
100 Hz to 6 kHz.  Nothing even close to the 2 cents accuracy claimed in the 
writeup.  I didn't check the temperature drift.  It shouldn't be too bad, 
but I know from another active-compensation circuit that you need good 
matching of the OTA pair.

   Ian