305-GHz Cascode SiGe HBT Power Amplifier With <i>L-C</i> Feedback Achieving <i>P</i> _sat of 8.3 dBm

A 305-GHz power amplifier (PA) fabricated in a 130-nm SiGe HBT BiCMOS technology with HBT <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$f_{t} / f_{max}$</tex-math></inline-formula> = 350/450 GHz and Aluminum metallization is presented. The PA employs 4-way combined 4 pseudo-differential cascode amplification stages with a capacitive feedback network between the collector of common base stage and the base of common emitter stage that counters the gain degradation by neutralizing the input loss and capacitance of common emitter stage resulting from the device parasitics, transit time related phase delay effects and the interconnect inductances in the layout especially due to the unavoidable interconnect between the output of common-emitter and input of the common-base stage. The PA achieves a measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{sat}$</tex-math></inline-formula> of 8.3 dBm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$OP_{1dB}$</tex-math></inline-formula> of 6 dBm and a peak small signal gain of 14.5 dB at 305 GHz while consuming 880 mW of DC power from a 4-V supply. The PA exhibits the highest <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P_{sat}$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$OP_{1dB}$</tex-math></inline-formula> and the highest small signal gain at 305 GHz among the PA's fabricated using SiGe HBT's with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$f_{max}$</tex-math></inline-formula> less than 500 GHz.