1. Show that the approximate diffusion equations derived for a constant electric field, (750.3A) and (750.4A), are also valid if E is not spatially constant but the region is quasi-neutral. This enables a derivation of a quantitative criterion on quasi-neutrality.
2. Show that the Kirchoff law used to derive (751.6C) and the charge-control equation for the terminal base current (751.7B) can be rigorously obtained by integrating the hole and electron continuity equations over the three-dimensional volume of the quasi-neutral base. This derivation will show that the terminal base current is indeed the majority carrier (electron) current due to recombination of the minority carriers (holes) injected by; the forward biased emitter-base junction with the majority carriers (electrons) in the base layer which are replenished by the electrons flowing into the n-base form the base terminal lead.