BJT - Bipolar Junction Transistors ,
i.e Transistors with a junction of p-type and n-type semiconductors.
These BJ Transistors are used in :
- 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
A PNP transistor in a radio boosts the relatively small signal from an antenna