Gate Diode Current Sensing for Device Temperature Estimation in GaN RF Power Amplifiers

This work presents a gate current sensing technique for RF power amplifiers suitable for estimating effects of self-heating in GaN HEMTs. For this, the gate-source Schottky diode is used as a temperature sensor which is modelled using a conventional exponential Schottky diode equation. The expressed model includes the temperature-dependent built-in voltage which is found to scale linearly with a coefficient of -9 mV/°C. Using this, an analytical expression is derived for the diode current which is sensitive to the internal temperature, experimentally validated with measurements. This model is capable of predicting the effects of self-heating in 10-W GaN-on-SiC RF power amplifier by using the diode characteristics extracted at DC, in a variation from 20° to 100°C.