A High-efficiency 3-Watt GaAs pHEMT X-band MMIC Power Amplifier

This paper presents the design and the fabrication of an 8.5-11.5 GHz fully-integrated monolithic microwave integrated circuit (MMIC) power amplifier (PA). Using a low cost 0.25-mu m AlGaAs-InGaAs pHEMT process, this three stage PA implemented a reactively matched class AB technique to obtain broadband performance, high gain and high efficiency within a compact size. It was designed by engineering the load and source fundamental impedances for the highest PAE as well as controlling the second harmonic load termination. The measurement results of this PA in the frequency range of 8.5 11.5 GHz show a small-signal gain of 33 dB, a maximum input return loss (S-11) of -13 dB, a maximum output return loss (S-22) of -15 dB, and a 35 dBm output power with the corresponding power added efficiency (PAE) of 45 49% in the CW-mode operation. To the author's knowledge, this is the first GaAs PA ever reported which achieves the combination of efficiency, output power and gain performance in the X-band frequency range.