Squarerooting transistors.

Christopher List Christopher_List at sonymusic.com
Thu Apr 4 14:55:09 CEST 1996

Howdy DIYers,

I'm building this Serge-like mixer panel using hot-off the press SSM2164 quad 
VCA's. One  2164 per mixer channel. One VCA for the gain, two for the pan, and 
one for the gain CV. The problem is that they have an exponential voltage 
control input and I want the control of the gain CV to be linear. 

What I'm wondering is this: You can use two transistors to create an 
exponential current source from a linear input voltage. Is there a way to wire 
them in reverse so that you have a square-root (reverse log?) voltage source 
from a linear input current? 
Just a point in the proper direction would be helpful.

- Thanks,

Note that for the 2164, 0v in = 0 attenuation, and 5 or 10 v in = max 
attenuation. If I can't find an easy way to do this I'll just "waste" one of 
the VCA's on the 2164 and use a 3080 or something instead.

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