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 g
m
and R
ds
have been obtained as well. In addition, the critical noise parameter T
d
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.