VCA the OTA way

To recap, an OTA has a voltage input, control current input, and output current. An obvious synth application would be as a VCA. The challenge is a VCA is voltage-controlled, not current-controlled. Also the output current must turn into an output voltage, which isn't a huge deal since that really just requires a resistor. When I talk about VCAs, I am referring to the amplifier that is controlled by the envelope to shape the sound, creating the illusion of a note playing. Final level controls especially in polysynths can also be VCAs and use OTAs, but those are boring.

The following is a list of synths using the 3080 or 3280 OTAs for the VCA:

CA3080: Moog Taurus (I & II), Prodigy, Rogue, Opus 3, (Realistic) MG-1, ARP Odyssey, Octave CAT
CA3280: Sequential Circuits Pro-One

Not all synths use OTA chips for the VCA. Roland mostly used the BA662 which is a VCA rather than OTA. Also many later synths (especially polysynths) used SSM or CEM chips for the VCA. Korg synths (at least the MS-10 & MS-20) use a different solution. In conclusion, if you don't like OTAs, you don't like America.