Operational transconductance amplifier

An operational transconductance amplifier (OTA) is an amplifier whose differential input voltage produces an output current.

DIY OTA
OTA can be made from matched-pair BJTs.

Data sheets

 * Operational Transconductance Amplifiers (OTA) at Aaron D. Lanterman's Synth DIY Datasheet and Ap Note Collection (Archive.org)

Projects

 * VCF-1 by Thomas Henry