An X-Band Low-Voltage GaN HEMT Stacked Power Amplifier Operating in Class-J with Active Second Harmonic Injection

This paper describes a stacked power amplifier (PA) operating in Class-J mode over 9.0–10.0 GHz in which the efficiency of the PA is enhanced by active second harmonic (2f) injection. Sony’s GaN HEMT technology is employed to obtain high power at low supply voltage. A small-signal gain of 24.0 dB with continuous-wave saturation output power of 34.2 dBm and power-added efficiency of 56.2% together with a final stage drain efficiency of higher than 70% are achieved at 9.5 GHz at a supply voltage of 5V. The chip size is 1.2 mm2.