A methodology to characterise the virtual gate effect in a power amplifier

An experimental method to characterize the virtual gate effect in radio-frequency (RF) power amplifiers (PAs) based on high-electron-mobility transistors (HEMTs) is presented. The experimental setup ensures that the GaN device in an amplifier is at the same temperature and trap state every time the experiment is repeated. An algorithm is proposed to estimate multiple trapping time constants simultaneously from measured DC drain current transients of the PA in response to pulsed RF excitation. We observe that the time constants of the device recovery time remain constant over a range of power levels and are related to the shape of the load cycle of the device.