A 4-7 GHz Broadband Cryogenic GaAs mHEMT LNA with a Flatness Gain Variation of ±1.2 dB

In this paper, a cryogenic low noise amplifier (LNA) consisting of three common-source stages is designed in a 70-nm GaAs metamorphic high electron mobility transistor (mHEMT) process for quantum computer applications. By using a cryogenic HEMT model, this LNA operates at 4 K and features wide bandwidth and high gain. It applies a filter input matching network and a bandwidth extension topology in the input and interstage matching, respectively. Characterized over the frequency range of 4 to 7 GHz, the LNA demonstrates a high gain level of 28.6 ± 2 dB with power consumption of 7.2 mW. In the low-power mode, it still maintains a gain level of 21.3 ± 1.2 dB with power consumption of 1.9 mW.