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.