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305-GHz Cascode Power Amplifier Using Capacitive Feedback Fabricated Using SiGe HBT’s with fmax of 450GHz
A 305-GHz power amplifier (PA) fabricated in a 130- nm SiGe HBT BiCMOS technology with HBT ft / fmax = 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 ~4 dB and a 4-way power combiner at the output. The PA achieves a measured Psat 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 PAEmax of 0.39%. The PA exhibits the highest Psat and OP1dB at 290 GHz, and the highest small signal gain at 305 GHz among the PA’s fabricated using SiGe HBT’s with fmax less than 500 GHz.