Low-frequency noise sources in bipolar junction transistors

Low-frequency noise measurements are made on specially fabricated silicon tetrode planar transistors. The measurements show the existence of three distinct sources of excess noise: a 1/ noise source associated with the surface; a l/ noise source associated with the active base region; and an anomalous burst noise source associated with the forward-biased emitter-base junction. Burst noise which is present in many transistors is a random fluctuation of the dc currents of the transistor. The terminal characteristics of these various noise sources are described and a modified noise model is presented which is useful for low-frequency noise calculations.