[sdiy] Log/exp conversion

[David Reichert]

Hi Everyone,
 
I’m somewhat new to the whole synth/DIY thing, hope you don’t mind a
relatively rookie question.
 
Anyway, I’ve been working on a VCO design, but still need to work in the
log conversion bit for the 1V/oct. Seems that everything I’ve tried so
far doesn’t work. All of my transistor circuits seem to remain linear,
even in the 0-700mV range. Does anyone know of a good source of
information on the design of these converters?
 
The design is based around a CA3080 OTA. I read somewhere that PNP
transistors are required for OTA designs. Is this true?
 
Thanks and Merry Christmas,
Dave
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