Non-ideal Characteristics
As with the standard op-amp, practical OTA's have some non-ideal characteristics. These include:
- Input stage non-linearity at higher differential input voltages due to the characteristics of the input stage transistors. In the early devices, such as the CA 3080, the input stage consisted of two bipolar transistors connected in the differential amplifier configuration. The transfer characteristics of this connection are approximately linear for differential input voltages of 20 mV or less. This is an important limitation when the OTA is being used open loop as there is no negative feedback to linearize the output. One scheme to improve this parameter is mentioned below.
- Temperature sensitivity of transconductance.
- Variation of input and output impedance, input bias current and input offset voltage with the transconductance control current Iabc.
Read more about this topic: Operational Transconductance Amplifier