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Question
What is UJT  PNP, NPN transistor & working principles?
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
PNP configuration
NPN AND PNP
PNP transistor:

When common base connection of a NPN transistor.In the
forward bias connection of the first PN junction ,it causes
the majority charge carrier(holes) in the P-type ,flow from
emitter to the base region .This constitutes the emitter
current (Ie) in the transistor.As these majority carrier
(hole) cross in to N-type base .They are combine with the
electron .Only the few hole (i.e less than 5%) combine with
the electrons ,because the base of this transistor is
lightly doped and very thin .Expects those holes ,all other
i.e More than 95% cross in to the collector region.This
constitutes collector current (Ic). In this process ,almost
the whole emitter current (holes) flows into the collector
region .So in this transistor ,current conduction in the
circuit is by holes.

Ie=Ic+Ib
Where ,
Ie=emitter current,
Ic=collector current and
Ib=base current



NPN transistor:
When common base connection of a NPN transistor .In the
forward bias connection of the NP junction,it causes the
majority charge carrier(electrons)in the N-type ,flow from
emitter to the base region.This constitutes the emitter
current(Ie) in the transistor.As these majority
carrier(electrons)cross in to the P-type base.They are
combine with the holes.Only the few electrons(i.e less than
5%) combine with the holes ,because of this transistor is
lightly doped and very thin.The remainder i.e more than 95%
cross into the collector region.This constitutes collector
current (Ic).In this way the whole emitter current
(electrons)flows into the collector region .So in this
transistor, current conduction in this circuit is by electrons.
 
Is This Answer Correct ?    8 Yes 3 No
Saiful Islam
 

 
 
 
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