A SPICE Model of Operational Amplifiers for Electromagnetic Susceptibility Analysis

This article proposes a macromodel to predict the nonlinear behavior of operational amplifiers having their baseband signal affected by out-of-band disturbances, such as those caused by electromagnetic interference. Like any opamp macromodel, the one proposed in this work was developed with the purpose of not sharing neither the technology parameters nor the circuit topology of the real device. Besides the baseband macromodel, the proposed solution comprises a high frequency equivalent circuit that propagates the out-of-band signals, and a nonlinear model to account for their demodulation. The proposed solution is suitable for any SPICE-like simulator. It does not affect the simulation performance, meaning the simulation time, the simulation accuracy and it does not cause any convergence issue. This article shows in detail the macromodel, the method to calculate its parameters as well as its experimental validation, which was obtained comparing the model predictions with the results of the measurements carried out on a commercial device.