+1 vote
Construction of the both the transistors is simple by the way of doping we do. But the operation is quite confusing.
asked May 11, 2016 in Electro-Communication by T.PRATHIBA
retagged May 12, 2016 by slow_learner | 424 views
+1 good question

1 Answer

+1 vote
Selected Ans.

BJT - Bipolar Junction Transistors , 

i.e Transistors with a junction of p-type and n-type semiconductors.

These BJ Transistors are used in :

  • Switches
  • Amplifiers or oscillators

Both PNP & NPN Transistors have same working principle but there are changes in :

  • How they are biased
  • Polarity of power supply

In simple words , in PNP transistors all voltages and current are reversed as when compared to NPN transistor.

NPN Transistor :

  • Current flows from Collector to Emitter
  • Electrons are important carriers


  • Most common use of NPN is switches where it goes ON(Saturation Mode) and OFF(Cut off Mode) in high power devices

PNP Transistor :

  • Current flows from Emitter to Collector 
  • Hole (positively charged) are important carriers

Uses :
A PNP transistor in a radio boosts the relatively small signal from an antenna

answered May 12, 2016 by transformer
selected May 12, 2016 by T.PRATHIBA
simple and clear answer. Thank you :)
its good to hear good comments..thanks