[sdiy] LM13700 VCA circuit

[Ryan Williams]

ahh, I see it now. much simpler than I thought, but I wasn't going about 
solving it the right way. Should have read your doc first...

thanks again!

James Patchell wrote:
> It does cancel out...or nearly so...it is so close, that one can say 
> that it does.  If you look at equation (1) in that doc...which has the 
> transfer function,  you will note that the denominator is "1 + gm * 
> R44....as long as gm * R44 >> 1, then you can assume that the tempcos of 
> the two Gms wil cancel out...which it turns out...they do in practice (I 
> have measured it to make sure)....
> 
> At 02:56 AM 9/20/2004 -0500, Ryan Williams wrote:
> 
>> 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
>>