Perspectives on GaN MISHEMT Power Amplifier versus Positive Gate Bias Instability

In this work, we discuss whether a positive gate bias instability (Delta Vth) issue hampers a GaN MISHEMT in power amplifier (PA) applications. Two aspects are evaluated: (1) the safe gate modulation range of a GaN MISHEMT that is free of Delta Vth, and (2) the gate modulation range of a PA in linear operation. The analysis shows that the two ranges have a significant overlap, meaning that a linearly operating MISHEMT PA can be well designed to avoid the positive Delta Vth issue.