Difference Between NPN and PNP Transistor with Operation

Difference Between NPN and PNP Transistor: A transistor, specifically a bipolar junction transistor (BJT), is a semiconductor device featuring three terminals, three layers, and two junctions. Its primary functions within electronic circuits include serving as a digital switch and amplifier.

Difference Between NPN and PNP Transistor Overview

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Difference Between NPN and PNP Transistor

What is NPN Transistor?

Operation of the NPN transistor

• A small voltage between the base and emitter propels electrons from the N-type emitter to the P-type base.
• Some electrons traverse the base and enter the N-type collector region.
• A voltage between the emitter and collector attracts the electrons into the collector, creating a collector current regulated by the base current.
• The transistor amplifies by transforming the small base current into a larger collector current.
• The base current dictates whether the transistor is off (cutoff), on (saturation), or in an intermediate state (active region).
• The transistor amplifies or switches signals by controlling the collector current with the base current.

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What is PNP Transistor?

Three terminals of the PNP transistor

1. Emitter: This region provides charging carriers to the collector, and the emitter sends charge carriers to the collector through the base region.
2. Collector: This region collects the majority of charge carriers released by the emitter.
3. Base: This region triggers and regulates the amount of current flowing from the emitter to the collector. The accompanying image illustrates the symbol and structure of the PNP transistor.

Operation of the PNP transistor

1. A small negative voltage between the base and emitter propels holes from the P-type emitter into the N-type base.
2. Some holes traverse the base and enter the P-type collector region.
3. A voltage between the emitter and collector attracts the holes into the collector, creating a collector current controlled by the base current.
4. The transistor amplifies by transforming the small base current into a larger collector current.
5. The base current dictates whether the transistor is off (cutoff), on (saturation), or in an intermediate state (active region).
6. The transistor serves to amplify or switch signals by controlling the collector current with the base current.