Schema equivalent du transistor allie resistance de base et tension de bruit ramenee a l'entree du transistor

Abstract

Minority carriers injection in the base of a transistor modulates the conductivity and a dynamic base resistance must be added to the emitter-base diode impedance of the equivalent circuit. This resistance is strongly current dependent. A study of the transistor equivalent circuit at a frequency higher than the alpha cut-off frequency shows the current dependence of this element. Distributed elements can be located from a physical model and an equivalent circuit accounts for the observed phenomena in the complex plane. This method allows us to calculate from these measurements a noise voltage. This voltage is added to the input of the transistor which can now be considered noiseless.