A temperature noise model for extrinsic FETs

A resistor temperature noise model for FETs has been successfully applied to extrinsic FETs to predict the frequency dependence of minimum noise figure F/sub min/ and associated gain G/sub Aopt/. The model gives a fixed relationship between F/sub min/ and G/sub Aopt/ with one fitting parameter T/sub d/. An extensive comparison to published results shows that the majority of FETs can be modeled with effective T/sub d/ values (the temperature of the output resistor) between 300 and 700 K for all of the frequencies (8 to 94 GHz), gate lengths (0.8 to 0.1 mu m), and material types examined. The analysis shows that InP-based MODFETs exhibit significantly lower F/sub min/ and higher G/sub Aopt/ than conventional and pseudomorphic GaAs-based MODFETs of the same gate length. The results suggest a high F/sub max/ is a key factor for low noise figure.<
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