On-Wafer Large-Signal Model Verification

The accuracy of a semi-empirical model to represent the nonlinear behavior of high frequency transistors is investigated. To verify model accuracy different types of unipolar transistors were modeled and examined with error corrected large-signal on-wafer measurements. The validity of the model is shown to depend directly upon the measurement accuracy of the small-signal scattering parameters. Bias dependent small-signal S-parameter surfaces are shown on 3-dimensional Smith/Polar charts. EEsof´s empirical model EEFET1 is shown to accurately model nonlinear performance of Gallium Arsenide MESFET´s but not pseudomorphic MODFET´s. Accurate prediction of output transconductance is critical for representation of large-signal gain and output power. The EEFET1 model fails to predict bias dependent characteristics of MODFET´s, resulting in an over prediction of large-signal gain and output power.