[sdiy] Log converters

[David G. Dixon]

Walker,

That's basically what I use the SSM2164 for (actually the Coolaudio V2164,
available cheap at Small Bear Electronics).  It is a quad VCA which converts
a linear control voltage to an exponential current attenuation (negative
gain) at 33mV/dB.  If you put the CVs through one VCA and apply the "magic
voltage" of 298.45mV to it, then put this current through an inverter with a
gain of about 54.5%, you get more or less perfect tempco into the bargain,
without a tempco resistor.  It makes a very nice substitute for the
traditional matched transistor pair and tempco resistor.

Email me for details.

> Any of yall ever use any kind of IC for log conversion or exponential
> current source?
> 
> I'm looking at this; not intended for CV application.