A simplified theory of the p-i-n diode

A simplified theory of the p-i-n diode is developed for the case of heavy injection in the base, and light injection in the end regions. The current I is taken as the fundamental parameter. The carrier densities n₁ and n₂ at the base boundaries are given directly as functions of the current I by means of simple approximate expressions. The approximation improves with increasing base width and increasing current. It is always within 15% of the correct value for base widths of about 2 diffusion lengths or higher. The accuracy is much better still on the voltage drop across the device, as calculated from the approximate equations for the carrier densities within the base.