Descret OTA & Simulator

[Michael B. Irwin]

I modelled the CA3080 OTA in Electronics Workbench (demo version) using
the 2N3904 and 2N3906 transistor models, with diode-connected
transistors used for the diodes in the current mirrors. Seems to work,
used it to model a VCA and a 6-stage phaser, but I do not know how
closely it matches the real thing. ( The Moog VCF also worked-it would
oscillate with a nice sine wave when the resonance was turned up).  The
National Semiconductor website has a PSpice model for the LM13600. I
have used this in EWB but be careful of the pinout - there is no OTA
icon in the menu so I adapted a non-standard pinout for the 7-terminal
op amp icon.