On Certain Noise Properties of Field-Effect and Bipolar Transistors

In the noise modeling of FET´s, it has been previously shown that the allowed values of T_min and N for an intrinsic chip have to satisfy inequality 1les4NT₀/T_minles2. This inequality is shown in this paper to be valid for a much more general class of noisy two-ports. It is shown that the noise model of a FET with gate leakage and the noise model of an HBT satisfy this inequality. Close-form exact expressions for the noise parameters of a FET with gate leakage and of an HBT are given. Also, close-form approximate expressions valid at low and high frequencies for the noise parameters of a FET with gate leakage and of an HBT are given. Simple equivalence relations between these two sets of noise parameters are established.