(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 »|