[sdiy] LM13700 VCA circuit

[Ryan Williams]

hi jim,

thanks for the reply. The one you are using seems different without the 
extra opamp. I saw that circuit reccently on a vca circuit but wasn't 
able to solve the circuit equations so that everything cancels out, but 
maybe I did something wrong? so I didn't want to build it without 
understanding it first.

-ryan

James Patchell wrote:
> Yes, it will, in fact...it has already been done...The only difference 
> between what you did and what somebody else did was you have some extra 
> gain in the feedback loop that the linearizing OTA is in.  I used the 
> circuit I found in my temperature compensated VCO's (circuit in the 
> following url)
> 
> http://www.oldcrows.net/~patchell/synthmodules/100-1007.pdf
> 
> If you look on page 5 of that doc you will see your circuit sans the 
> extra opamp...
> 
> I measured about 0.1 % linearity...which is pretty darn good...