Comparative performance of the equivalent noise resistance of low-noise microwave FETs

Among the frequency-dependent noise parameters F/sub 0/, /spl Gamma//sub 0/ (magnitude and angle) and r/sub n/, the value of F/sub 0/ represents the minimum noise contribution of an active device in absence of any noise mismatch at the device input (which can be obtained at a single frequency), while r/sub n/ is a measure of the noise figure degradation upon departure from the optimum value of the noise source reflection coefficient. As such, the performance of r/sub n/ is of fundamental importance for the circuit designer when a broad-band low-noise amplifier has to be realized. In this paper, a comparative analysis and related comments are presented on the behavior of this noise parameter for different low-noise device types which have been characterized and modeled in our lab over the last ten years.