Improved analysis of the harmonic and intermodulation performance of operational amplifiers

Simple formulas are presented for the nonlinear voltage-controlled current sources of operational amplifiers with strong inversion MOSFET, weak inversion MOSFET, JFET and bipolar input transistors, and are shown to fit the nonlinearities very well. Furthermore, closed-form expressions are derived for the output signal and intermodulation product levels of an operational amplifier excited by a multisinusoidal input signal. The results are presented in a form suitable for predicting the influence of the nonlinear voltage-controlled current source on the performance of electronic circuits incorporating operational amplifiers.