HIGH POWER-ADDED EFFICIENCY AND LOW DISTORTION GAAS POWER FET EMPLOYING SPIKE-GATE STRUCTURE

A GaAs power FET employing a spike-gate structure was developed for th e high efficiency and low distortion operation under the extremely low supply voltage of 1.5 V. This spike-gate FET is featured by an unique gate structure that has almost zero effective gate length. The spike- gate provides both the low on-resistance of 2.2 R mm(-1) and the low d rain conductance of 5 mS mm(-1). Maximum frequency of oscillation (f(m ax)) is over 30 GHz that is estimated from S-parameter under the suppl y voltage of 1.5 V. The decrease of the f(max) is smaller for the spik e-ate FET than for the conventional one as the decrease of supply volt age. In pi/4-shift QPSK modulation system, the implemented device achi eved the output power of 31.0 dBM with 52% power-added efficiency and -51 dBc adjacent channel leakage power at the frequency of 925 MHz und er the drain supply voltage of 1.5 V. (C) 1997 Elsevier Science Ltd.