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4 GHz measurements have been made of the noise temperature of Bell Laboratories microwave GaAs f.e.t. amplifiers cooled to liquid-nitrogen temperatures (78 K). An optimum noise temperature of about 30 K (0.4 dB noise figure) was obtained, compared with the room-temperature value of 152 K (1.8 dB).
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Miller et al. (1977) studied this question.
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