Equivalent gain analysis for nonlinear operational amplifiers

For low-voltage, low-power circuit design, the linear model for operational amplifiers is insufficient to accurately predict the static and dynamic behavior of the circuit. This paper introduces a nonlinear model for operational amplifiers based on amplifiers' DC transfer characteristic. By using this nonlinear model, the behavior of an operational amplifier with feedback network can be described more accurately. Equivalent open-loop gains of the operational amplifier for several common closed-loop applications are studied. These equivalent gains can help identify the nonlinearities in the close-loop amplifier and determine the performance of the circuit.