Transistor noise theory in the Middlebrook limit of high injection

Abstract

Transistor noise in p- n- p transistors at high injection is calculated for a one-dimensional model for arbitrary values of p 0( w B )/ p 0(0), where p 0(0) is the hole concentration on the emitter side of the base region and p 0( w B ) the hole concentration on the collector side of the base region, and it is found that additional terms occur in the noise expressions. The results are then applied to the low-frequency case. The equivalent circuit of the transistor is calculated for the Middlebrook limit, where p 0( w B )/ p 0(0) attains a limiting value, and it is found that this circuit is greatly simplified in comparison with the case p 0( w B )/ p 0(0) < 1. Finally the correlation impedance Z cor of the transistor noise is calculated at relatively low frequencies and it is found that the theory cannot explain the large values of Z cor observed by Tong and van der Ziel.