I just have a few questions on the physical operations of the BJT. 1) Van Zeghbroeck's online book says, The carrier densities vary linearly between the boundary values as expected when using the assumption that no significant recombination takes place in the quasi-neutral regions. Why would the carrier density vary if there is no recombination. What causes the minority carriers to drop down in density as you move across the junction. 2) If the excess minority carrier concentration is the highest at the EBJ and lowest at the CBJ then how does the majority of the electrons get collected at the collector? At the CBJ the electron density is only np0 not np0*e^VBE/VT? How does that work? I thought most of the injected electrons from the emitter is suppose to be collected by the collector? Thanks.