Monolithic X-band heterojunction bipolar transistor power amplifiers

Compact, single-stage HBT power amplifiers with on-chip impedance matching and bias circuits were fabricated on MOCVD-grown wafers in two circuit designs. The first design produced 1.0-W CW output power at 9 GHz with 5.8-dB gain and 40% power-added efficiency. The size of this monolithic chip was 1.9 mm*0.7 mm. The second (larger) amplifier design produced 2.5-W CW output power at 8 GHz with 6.1-dB gain and 39% power-added efficiency. The size of this amplifier chip was 1.9 mm*1.7 mm. Each amplifier had about 10% gain bandwidth. An output power of 5.3 W CW was obtained by parallel connection of two monolithic chips with 4.3-dB gain and 33% power-added efficiency. The high power density (>2.0 W/mm of emitter length) of HBTs (heterojunction bipolar transistors), together with the monolithic implementation of lumped element matching circuits, resulted in significant reduction of amplifier chip size in both designs.<>