GaN HEMT Characterization for High-Efficiency Power Amplifiers

High-efficiency power amplifier (PA) is particularly important for next-generation communication systems. Gallium Nitride (GaN) devices are desirable for such applications due to their excellent capabilities such as high power, high efficiency, and high gain with high-voltage operation. In order to further improve the efficiency of the GaN HEMTs, an accurate evaluation of the drain-current source (current generator in general) is essential, because knee voltage strongly affects attainable efficiency. Recently, a time-domain measurement setup working at low-frequency was proposed. This characterization method is capable of measuring RF characteristics such as output power and drain efficiency as well as observing dynamic load lines under realistic large-signal operation. In this talk, we will show several evaluation results of GaN HEMTs for validation of RF-performance improvement. Furthermore, we describe the influence of gate-voltage clipping behavior and the knee-voltage effects on drain efficiency in case of various class of operations such as class-F and inverse class-F. which demonstrates the effectiveness of the characterization method.