The design of a broad-band monolithic cryogenic low-noise amplifier (MMIC LNA) in the Q band, aimed to be used in radio-astronomy receiver front-end modules is presented. A 70 nm gate-length GaAs mHEMT process from OMMIC foundry is used to manufacture the amplifier. An accurate model for the minimum noise bias point of the transistor has been obtained at room temperature. The amplifier design is based on a four stage monolithic common source transistor configuration. At 300 K, the amplifier shows an associated gain of 28 ± 1.1 dB and an average noise temperature of 145 K with a minimum noise temperature of 101 K at 45 GHz tested on wafer. When cooled down at 15 K, the average noise temperature is 18.4 K with a minimum of 13.5 K and 27.3 dB of associated gain. The DC power consumption is extremely low, 4.1 mW, at cryogenic temperature
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