Impact of Input Nonlinearity on Efficiency, Power, and Linearity Performance of GaN RF Power Amplifiers
The impact of input nonlinearity due to the nonlinear CGS-VGS profile on load harmonic tuned power amplifier (PA) performance is qualitatively discussed. It is experimentally validated by pulsed vector load pull measurements that both Class B and Class F PA operation are quite sensitive to the source second harmonic (Z2S) termination with an efficiency delta of ~40%. In contrast, Class F-1 PA shows relatively robust performance with an efficiency delta of ~10% versus Z2S terminations. Thus, we identify the ‘good’ and ‘bad’ design space of Z2S terminations on the Smith chart for load harmonic tuned PA classes. In addition, this paper identifies a design space continuum for Z2S terminations other than a short for Class F-1 PA which results in consistent efficiency, output power, and improved linearity.