Intrinsic capacitances effects on the accuracy of the large-signal switch-based GaN device model

This paper assesses the impact of two modelling approaches for the nonlinear drain-source and gate-drain capacitances in a switch-based GaN HEMT model on predicting large-signal and switching-mode device performance. The extracted values for these intrinsic capacitors, derived from measured S-parameters in deliberate bias points, are modelled by a zeroth and first order approximation. Using these approximations in an in-house developed large-signal switch-based device model for GaN HEMTs, their effects on modelling accuracy of switching-mode operation at microwave frequencies are shown by comparing simulation and load-pull measurement results for inverse class-F operation. Whereas a zeroth order approximation is confirmed to provide good accuracy for both output power and efficiency prediction in saturation, the study shows that modelling the gate-drain capacitance with a linear equation instead of constant values extends the application range of the switch-based model to the linear region. Good agreement between large-signal simulation results and load-pull measurements in this operation mode has been obtained.