30 January 2018

Difference between NPN and PNP transistor

Nowadays, the NPN transistor is the most commonly used of the two types. It can be used for amplification and switching application, NPN has higher electron mobility than PNP. Therefore, NPN bipolar transistor is often more favored compared to PNP transistor. Yet they have significantly different characteristics.

Main Difference :

The main difference between them is in their internal structure and also electrical current flow direction. 

Another main difference between these two types of transistors is that the holes are more important carriers for PNP transistors, while electrons are more important carriers for NPN transistors. 

This is all about the main difference between transistor NPN and PNP which are used to design electrical and electronic circuits and various applications. 
So now let us check some other significant differences are described with the help of comparison between them.

Difference between NPN and PNP transistor

  • NPN called for Negative-Positive-Negative type transistor and PNP called for Positive-Negative-Positive. 
  • The one p-region is to sandwiched by two n-region, its called NPN transistor with two p-region sandwiched one n-region, called as PNP transistor.
  • Both transistors are composed of different materials.
  • NPN transistor is turned ON when the electron enters into the base, and the PNP transistor is turned ON when holes enter into the base.
  • The current flows from the collector(C) to the emitter(E) in NPN transistor, while in a PNP transistor, the current flows from the emitter(E) to the collector(C).
  • In an NPN transistor majority charge carrier electrons and minority charge carrier holes, while  In a PNP transistor majority charge carrier holes and minority charge carrier electrons.
  • In an NPN transistor, the switching time is faster while PNP transistor switching time is to be lower.
  • The ground signal of the NPN transistor is low, while high in PNP transistor.
  • NPN transistor sources it, and PNP transistor sink current. 
  • The emitter-base junction of both the transistor NPN and PNP is connected in a biased forward direction.
  • Both the NPN and PNP transistor base junction is connected in reverse bias.
  • For low current applications, BJT is preferred while MOSFET is suitable for high power functions. 

Difference between working principle :

  • NPN transistor: When the current is increased to the base terminal, transistor switches ON and it performs from the collector terminal to the emitter terminal. When reducing the current to the base, the transistor switches ON and the flow of current is so slow. 
  • PNP transistor: When the current exists at the base of the PNP transistor, and then the transistor turns OFF while there is no current flow at the base of the transistor then the transistor is switched ON.