EMT 297 & 272 (PHYSICS OF SEMICONDUCTOR)SEM 2 2014/2015ASSIGNMENT

DUE DATE: Wednesday, 6th May 20151. Illustrate and analyze the IV graphs for PNP BJT at common base and common emitter configuration.

Ic remains constant even VBC down to 0V.A small change in IB, give rise to a much larger Ic.

2. Based on your understanding on PNP BJT at common base configuration, what we should do to make Ic=0. Distinguish your answer using minority carrier distribution in the base region.

to reduce ICto 0 apply a small forward bias (about 1V to B-C junction to the BC junction [in the saturation mode]) fig. (b)The forward bias will increase the hole density at x=Wto make it equal to that of the emitter at x=0 (horizontal line)

The hole gradient at x=W& ICwill reduce to 0

3. From your opinion, recommend which BJT configuration is often most used in circuit application. Please include your reasons.

Common emitter is much more preferred for circuit application because, a small change in base current IB can produce larger collector current.