A GaAs linear power amplifier operating with a single 3-V supply has been developed for 5.8-GHz ISM band applications. Two kinds of refractory WNx/W self-aligned gate MESFETs, a P-pocket MESFET and an asymmetric MESFET with a buried p-layer (BP- MESFET ) have been compared in terms of DC characteristics, small signal characteristics and power performances at 5.8 GHz. To obtain both high gain and high efficiency in the case of single 3-V supply operation at 5.8 GHz, we used a highly efficient and linear P-pocket MESFET for the output-stage power FET and a high-gain asymmetric MESFET with a buried p-layer (BP- MESFET ) for the driver-stage FET. The bias condition for 1-mm output-stage P-pocket MESFET was set near class-AB, so as to obtain sufficient output power with high PAE. The two-stage power amplifier MMIC module which can include all matching and biasing circuits, has been designed and fabricated. The amplifier exhibits a high power gain of 17.9 dB and a high power-added efficiency of 25.7% with a sufficient output power of 18.7 dBm at the 1-dB compression point. This self-aligned gate GaAs MESFET technology is promising for near-future 5.8-GHz applications, because of such good power performance and good mass-producibility.

A GaAs power MESFET amplifier with a low-distortion, 10-dB gain-variable attenuator has been developed for 1. 9-GHz Japanese personal handy phone system (PHS). Independently of its gain, a very low 600-kHz adjacent channel leakage power (ACP) with sufficient output power was attained. In single low 2. 4-V supply operation, an output power of 21. 1 dBm, a low dissipated current of 157 mA and a high power-added efficiency (PAE) of 37. 2% were obtained with an ACP of -55 dBc.