(i)Symbolic representation

(ii)In this conventional current flows from base towards emitter, hence the arrow head on emitter is directed from B to E.

(iii) Sketch diagram

(iv) Working of NPN transistor

(a) The emitter-base junction is forward biased whereas the collector-base junction is reverse biased.

(b) The majority electrons in the emitter are pushed into the base.

(c) The base is thin and is lightly doped. Therefore a very small fraction (say 1%) of incoming electrons combine with the holes. Hence base current is very small.

(d) The majority of electrons are rushing towards the collector under the electrostatic influence of C-B battery.

(e) The electrons collected by the collector move towards the positive terminal of C-B battery.

(f)  The deficiency of these electron is compensated by the electrons released from the negative terminal of E-B battery.

(g) Thus in NPN transistors current is carried by electron both in the external circuit as well as inside the transistor.

(h) The relation between these current is given by

« Click Here for Previous Topic Click Here for Next Topic »

Click Here to Go Back to CBSE Class 12 Physics Semiconductor Electronics All Topic Notes

Click Here for CBSE Class 12 Physics All Chapters Notes

Mody University Apply Now!!

Leave a Reply