[sdiy] Multiplexed Expo Converter?

[Dave Manley]

JH. wrote:
>> The most common expo is a voltage to *current* conversion (for a VCO, 
>> with the current controlling the charge rate of the timing cap, or for a 
>> VCF, the OTA control current).  The chain you describe would have the 
>> expo output a voltage.  What products do this?  
> 
> Polysix and Trident

Time to look at some service manuals :-)

With a modern DAC, why bother with an expo, just have the DAC output the 
expo-law voltage and drive linear VCOs.  With a built-in frequency 
counter it would be easy to auto-calibrate.

-D