High Injection Modelling of a Junction Transistor

Abstract

A physical model has been proposed for characterizing the dependence of collector current on applied emitter-base voltage in a bipolar transistor from medium-to-high injection levels of operation. The inputs to this model are the doping profile and the structural and the material parameters of the transistor. The effective value of diffusion constant in the base region, the forward transit time and the Gummel number have been calculated using numerical techniques. The emitter-base voltage corresponding to a given value of collector current is obtained from Gummel's charge-control relation and base-widening theory.

The collector current versus emitter-base voltage curve shows a doubling of the slope at the onset of high injection level which fits well with experimental observations.

Indexing Terms:

• High-Level Injection BJT
• Injection Modelling