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Cryogenic Modeling of GaAs-pHEMT and its Application in Low-power MMIC CLNA Design for Radio Astronomy

The small signal equivalent circuit parameters of GaAs-pHEMTs have been extracted with a cryogenic probe station at both 300 K and 4 K. The drain bias current dependent performances of the critical parameters namely gm and Rds have been obtained as well. In addition, the critical noise parameter Td in the Pospieszalski noise model is determined as a function of drain current by fitting the simulated and measured noise of a prototype MMIC cryogenic low noise amplifier (CLNA) with the same process technology. Based on the cryogenic models established at the optimal low-power bias point, a cryogenic low-power MMIC LNA operating in the frequency range 2.5∼5 GHz was designed, fabricated and tested at 4 K. The cryogenic MMIC LNA achieved a gain greater than 22 dB and a typical noise temperature of 11 K with the power dissipation of only 1.2 mW. The results obtained indicated that the low-power MMIC amplifiers can be used in the large format integrated focal plane array receivers for the astronomy application.