A 600 GHz InP HBT amplifier using cross-coupled feedback stabilization and dual-Differential Power Combining

We report a 600 GHz amplifier with > 30 dB peak gain, based on 12 cascaded differential common-base (CB) stages, in a 130 nm InP HBT process. Three consecutive CB stages are grouped as a unit gain block, sharing a common bias current. Each CB stage is stabilized by cross-coupled capacitive feedback. Output powers from two differential branches are combined through a 4-way combiner, resulting in a 4× increase in power compared to a single single-ended output stage. On-wafer testing in WR-1.5 band (500-750 GHz) shows that the amplifier exhibits > 20 dB of gain up to 620 GHz, with +2.8 dBm of saturated output power at 585 GHz, while consuming 455 mW.