Experimental and theoretical noise analysis of microwave HEMTs

Low-frequency noise power and high-frequency noise figures in HEMTs (high electron mobility transistors) were measured and compared with calculations based on a one-dimensional noise model to characterize their low-noise properties. It was found that the drain noise current parameter Q in HEMTS is lower than that in GaAs MESFETs. The strong correlation between drain- and induced-gate-noise currents in HEMTs is due to the asymmetric distribution of noise generation along a channel, and the drain noise current is nearly canceled by those induced-gate-noise current. The intrinsic thermal noise from source and gate resistances is about 25% of the total output noise in the 0.25- mu m gate-length HEMT considered.>