Class-A SiGe HBT power amplifiers at C-band frequencies

We report on the first experimental investigations of the power-handling capabilities of SiGe heterojunction bipolar transistors (HBT's) at C-band frequencies. Multifinger HBT's in common-emitter (CE) and common-base (CB) configuration were matched using high Q matching networks. At a frequency of 5.7 GHz the CE and the CB class A amplifier exhibit a 1-dB compression output power of 18 and 20 dBm, respectively. A power-added efficiency (PAE) of more than 30% and a output power density of 1 mW/μm
²
at 4 V V/sub CB/ were observed.