A complete empirical large-signal model for high-power AlGaN/GaN HEMTs (GaN HEMT) utilizing an improved drain current (Ids) formulation with self-heating and charge-trapping modifications is presented. The new drain current equation accurately models the asymmetric bell-shaped transconductance (gm) for high Ids over a large range of biases. A method of systematically employing dynamic IV behavior using pulsed-gate IV and pulsed-gate-pulsed-drain IV datasets over a wide variety of thermal and charge-trapping conditions is presented. The composite nonlinear model accurately predicts the dynamic IV behavior, -parameters up to 10 GHz, and large-signal wideband harmonic behavior for a multitude of quiescent gate–source and drain–source biases as well as third-order intermodulation distortion (IM3).