A Cryogenic 2.9–8.6-GHz LNA With Bandwidth Extension Technique for Quantum Applications

This work presents a wideband and power-efficient cryogenic low-noise amplifier (LNA) for quantum computing. Based on the inductive source-degeneration topology, a lossy output-feedback transformer (OFT) generates two slightly damping conjugate poles, which broaden the 3-dB bandwidth at higher frequencies and maintain low-noise performance. In addition, an input-matching transformer (IMT) is adopted to guarantee the input-matching bandwidth. Fabricated in a 0.18-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS technology, the proposed LNA exhibits a peak gain of 9.24 dB with a 3-dB bandwidth ranging from 2.9 to 7.8 GHz at room temperature (RT) (300 K). The minimum measured noise figure (NF) is 2.24 dB. At cryogenic temperature (CT) (4 K), the LNA shows a measured peak gain of 14.23 dB with a 3-dB bandwidth from 2.9 to 8.6 GHz, and the minimum measured NF is 0.6 dB. The power consumption of the LNA is 10 mW. To the best of the authors’ knowledge, the proposed LNA offers the widest bandwidth at 4 K among CMOS LNAs with power consumption below 10 mW.