A new nonlinear model of EMI-induced distortion phenomena in feedback CMOS operational amplifiers

This paper deals with distortion phenomena induced by radio-frequency interference (RFI) in analog integrated circuits and it concentrates on the effects induced by RFI on the operation of feedback CMOS operational amplifiers (opamps). In particular, the paper describes a new nonlinear model, which makes possible the prediction of upset in the opamp output nominal signal when RFI is superimposed on the input nominal signals. Such a model can be employed when the transistors of the input differential pair are driven by RFI either in strong or weak nonlinear operation. Results of experimental tests performed on a Miller CMOS opamp connected in the voltage follower configuration are presented and compared with model predictions.