Answer Posted / thowsif_emerson_csm team
NPN Transistor :-
Just as in the case of the PN junction diode, the N
material comprising the two end sections of the NP N
transistor contains a number of free electrons, while the
center P section contains an excess number of holes. The
action at each junction between these sections is the same
as that previously described for the diode; that is,
depletion regions develop and the junction barrier appears.
To use the transistor as an amplifier, each of these
junctions must be modified by some external bias voltage.
PNP Transisitor:-The PNP transistor works essentially the
same as the NPN transistor. However, since the emitter,
base, and collector in the PNP transistor are made of
materials that are different from those used in the NPN
transistor, different current carriers flow in the PNP
unit. The majority current carriers in the PNP transistor
are holes. This is in contrast to the NPN transistor where
the majority current carriers are electrons. To support
this different type of current (hole flow), the bias
batteries are reversed for the PNP transistor.
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