AN ACCURATE FET MODEL FOR MICROWAVE NONLINEAR CIRCUIT SIMULATION

We propose an accurate FET model for microwave nonlinear circuit simulation, which has been modified from the Statz model. We have greatly enhanced the accuracy of both de and capacitance expressions, especially in the knee voltage region where I-ds begins to saturate. In the expression of dc characteristics, our model improves the accuracy by incorporating the drain-source voltage dependence of pinch-off voltage, the gate-source voltage dependence of knee voltage, and the nonsquare dependence of drain current against the gate-source voltage. The non-square-root voltage dependence of gate capacitances is considered as well. All modifications are simple and the parameter extraction is kept as simple as that of the Statz model. By using this model, good agreement has been obtained between simulated and measured characteristics of a GaAs FET. For the de characteristics and the S-parameters, each of estimated error is within 5% and 10%. The model accuracy has been verified by comparison of simulated and measured results of power amplifier performances over a wide range of operating conditions.