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.