A noise model for the distributed transistor

A transistor model having a distributed base region and distributed sources of noise is analyzed. An equivalent lumped-noise model is derived. The model includes all the conventional sources of shot noise and thermal noise in the base region. It is found that the transistor shot noise is uneffected by the distributed nature of the base. Mean-square thermal noise is found to be proportional to the real part of a complex base impedance. An excess noise source due to the distributed base is found but is shown to be negligible compared to thermal noise generated in the base. The distributed-noise model reduces to the conventional lumped-noise model at low frequencies.