Ultracompact Inductorless Noise-Canceling LNAs in 40-nm CMOS Achieving 2.2-K Noise Temperature for Qubit Readout
Mahesh Kumar Chaubey, Yeke Liu, Yin‐Cheng Chang, Po‐Chang Wu, Hann-Huei Tsai, Shawn S. H. Hsu
Abstract
This article presents two ultracompact inductorless low-noise amplifiers (LNAs) in 40-nm CMOS for cryogenic qubit readout. Both LNAs utilize an inverter-based input stage as the main amplifier, and LNA-I and LNA-II employ a complementary and common-source (CS) stage, respectively, as the auxiliary amplifier for achieving noise canceling (NC). LNA-I also incorporates self-forward body bias (SFBB) to counter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\text {th}}$ </tex-math></inline-formula> reduction and improve <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${r} _{\text {out}}$ </tex-math></inline-formula> during cryogenic operation, while LNA-II uses source-follower feedback(SFFB) to enhance gain and noise figures (NFs) without compromising input impedance matching. At room temperature (RT), LNA-I achieves a measured gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} _{21}$ </tex-math></inline-formula> ) of 25.6 dB and a minimum NF of 0.63 dB at 2 GHz. At 4 K, it demonstrates a measured gain of 29 dB and a minimum NF of 0.033 dB (corresponding to a noise temperature <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T} _{N}$ </tex-math></inline-formula> of 2.2 K), along with a 3-dB bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{\text {3 dB}}$ </tex-math></inline-formula> from 10 MHz to 3 GHz, while consuming 19.4 mW. LNA-II achieves a measured gain of 27 dB and a minimum NF of 1.16 dB at 0.5 GHz at RT. At 4 K, it demonstrates a measured gain of 30.2 dB and a minimum NF of 0.29 dB ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T} _{N}$ </tex-math></inline-formula> of 20 K), accompanied by a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{\text {3 dB}}$ </tex-math></inline-formula> from 20 MHz to 4 GHz and with a total power consumption of 10.8 mW. The circuit only occupies an active area of 0.018 and 0.0072 mm2 for LNA-I and LNA-II, respectively.