High power efficiency X-band GaAlAs/GaAs HBT

Excellent power performance from a common-emitter GaAlAs/GaAs HBT (heterojunction bipolar transistor) at 10 GHz is reported. Record high added efficiency of 67.8% and 11.6-dB associated gain were obtained, with 0.226-W output power. HBTs of various sizes were tested, and 55% added efficiency and 10-dB associated gain were obtained regularly. From the largest available device 0.63 W with 8-dB gain was obtained. The base current crowding effect does not appear in the HBTs tested. The operation of the HBT is analyzed and shown to be close to that of the class-B amplifier. The collector-current behavior with respect to the power level is explained. Harmonic content is found to be very low. Compared with other solid-state power devices at 10 GHz the HBT demonstrates the highest added efficiency and associated gain at high-output-power condition. In addition, the low HBT input Q factor eases broadband matching, making it the best candidate for microwave power application.<
>