Operational transconductance amplifier

The first commercially available integrated circuit units were produced by RCA in 1969 (before being acquired by General Electric) in the form of the CA3080.

Like a standard operational amplifier, the OTA also has a high impedance differential input stage and may be used with negative feedback.

According to National Semiconductor, the addition of these diodes increases the linearity of the input stage by a factor of 4.

A second improvement is the integration of an optional-use output buffer amplifier to the chip on which the OTA resides.

This is actually a convenience to a circuit designer rather than an improvement to the OTA itself; dispensing with the need to employ a separate buffer.

It also allows the OTA to be used as a traditional op-amp, if desired, by converting its output current to a voltage.

Schematic symbol for an OTA with differential input. Like the standard operational amplifier, it has both inverting (−) and noninverting (+) inputs; power supply lines (V+ and V−); and a single output. Unlike the traditional op-amp, it has two additional biasing inputs, I abc and I bias .