A 173 GHz Amplifier With a 18.5 dB Power Gain in a 130 nm SiGe Process: A Systematic Design of High-Gain Amplifiers Above f(max)/2

摘要

A novel theory of stability for two-port networks is developed. Using this theory, a new method of designing amplifiers with a high-power gain working close to the maximum frequency of oscillation (f(max)) is proposed. Contrary to the existing amplifier design methodologies, in this method, the transistor capability of power amplification is fully utilized. This becomes more important at frequencies close to the f(max) where having a high-power gain is challenging due to the degraded activity of the employed device. The proposed method considers the modeling errors and process-voltage-temperature variations of the employed components in the design stage to ensure that the fabricated amplifier will be stable with a decent power gain even if the worst case variations and modeling errors happen. To show the feasibility of the proposed approach, a three-stage amplifier at 173 GHz, using bipolar junction transistors from a 130 nm SiGe process, is designed. The fabricated amplifier has a maximum measured power gain of 18.5 dB at 173 GHz. A similar three-stage amplifier using the same transistors with the same bias would give a maximum gain of 6.8 dB in simulation, assuming perfect lossless conjugate matching at input, output, and between stages. So it is clear that the fabricated amplifier achieves a significant improvement over the power gain.