[sdiy] Bernie Hutchins CA3080 VCA

[eq927 at freenet.carleton.ca]

Is this similar to the technique used by W. Jung (see Journal of Audio 
Engineering Society, April 1975, Vol.23, No.3)? The normal PNP + op amp 
current source is not used here - instead, the OTA is put in the 
feedback loop of an op amp. Positive control voltages feed a resistor 
connected to op amp (-) input, op amp output connects to OTA Vcc- (pin 
4), while OTA Iabc (pin 5) is connected to op amp (-) input. This forces 
a current linearly proportional to the control voltage into the Iabc 
pin. A diode clamp is used for reverse polarity protection.
Mike