305-GHz Cascode Power Amplifier Using Capacitive Feedback Fabricated Using SiGe HBT's with fmax of 450 GHz

A 305-GHz power amplifier (PA) fabricated in a 130nm SiGe HBT BiCMOS technology with HBT f(t)/f(max) = 350/450 GHz is presented. The PA employs 4 cascode amplification stages with capacitive feedback between the collector of common base stage and the base of common emitter stage that increases power gain of each stage by similar to 4 dB and a 4-way power combiner at the output. The PA achieves a measured P-sat of 7.5 dBm and OP1dB of 4.5 dBm at 290 GHz. The design reaches a peak small signal gain of 14.5 dB at 305 GHz. The circuit consumes 1008 mW DC power from a 4-V supply and achieves a PAE(max) of 0.39%. The PA exhibits the highest P-sat and OP1dB at 290 GHz, and the highest small signal gain at 305 GHz among the PA's fabricated using SiGe HBT's with f(max) less than 500 GHz.