A transistor (or bipolar junction transistor) is a three-terminal, three-layer and two-junction semiconductor device, used as the digital switch and amppfier in the electronic circuits.

A transistor consists of three layers of P-type and N-type semiconductor materials and the name of these layers are emitter, base and collector. The three terminals are taken out from these three layers.

Based on the arrangement of the semiconductor layers, the transistors are of two types as −

NPN Transistor

PNP Transistor

Read through this article to find out more about NPN transistor (BJT) and PNP transistor and the key differences between them.

What is NPN Transistor?

An NPN transistor is the one in which two layers of N-type semiconductor material are separated by a thin layer of P-type semiconductor material. Hence, in case of NPN transistor, the emitter and collector are of N-type while the base is of P-type. The symbol of the NPN transistor is shown in Figure-1.

What is PNP Transistor?

When a thin layer of N-type semiconductor material is sandwiched between two layers of P-type semiconductor material, the resulting transistor is known as a PNP transistor. In a PNP transistor, the emitter and collector are made of P-type semiconductor material while the base is made of N-type material. The circuit symbol of PNP transistor is shown in Figure-2.

Difference between NPN and PNP Transistor

The following table highpghts the key differences between NPN transistor and PNP transistor −

Conclusion

From the above discussion, it can be concluded that there are various differences between NPN and PNP transistors. Both of these transistors are widely used in different electronic apppcations pke in switching and amppfication, etc. Thus, the knowledge of these differences can help an inspanidual to select the right kind of transistor as per the exact requirements.