Double-doped power heterojunction FET for 1.5 V digital cellular applications

This article describes 1.5 V operation power performance of a double-doped AlGaAs/InGaAs/AlGaAs heterojunction FET (HJFET) for personal digital cellular phones. A 1.0 μm gate length HJFET exhibited 600 mA mm−1 maximum drain current, 260 mS mm−1 transconductance (gm) and 9.4 V gate-to-drain breakdown voltage. Operated with a drain bias of 1.5 V, a 28 mm gate width HJFET demonstrated 1.02 W (30.1 dBm) output power and 45.2% power-added efficiency with −50.3 dBc adjacent channel leakage power at 50 kHz off-center frequency. This excellent power performance under 1.5 V operation was discussed with a low on-resistance of 2.5 ohm mm as well as with linear gm characteristics around an operating bias point.