Electrothermal Transient Analysis of GaN Power Amplifier With Dynamic Drain Voltage Biasing

AM-AM distortion due to dynamic drain voltage biasing for a power amplifier (PA) has been precisely emulated by an electrothermal transient analysis. A transistor model of a 20-W gallium nitride field-effect transistor (FET) in the PA for the electrothermal simulation is composed of thermal equivalent circuits and the Angelov FET model. Radio frequency performances of the PA were simulated by the transient analysis of amplitude modulation input signals with modulation frequencies from 2.5 to 10 MHz. The simulation results showed that a temperature variation in the PA caused AM-AM hysteresis on the order of MHz, which was consistent with the results obtained from a theoretical analysis of the transient temperature.