[sdiy] Bernie Hutchins CA3080 VCA

[Ian Fritz]

Yes, it's the same as the W. Jung technique. Definitely not a misdrawing.


At 04:23 PM 12/19/2001, eq927 at freenet.carleton.ca wrote:
>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