Working of PNP transistor

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A PNP transistor is a type of bipolar junction transistor (BJT) that consists of three layers of doped semiconductors: a p-type emitter, a n-type base, and a p-type collector. The base is very thin and lightly doped, while the emitter and collector are heavily doped.

Working of a PNP transistor:

A PNP transistor works by amplifying or switching electrical signals. It does this by controlling the flow of current between the emitter and collector terminals.

When a PNP transistor is forward-biased, the emitter-base junction allows holes to flow from the emitter to the base. The base is very thin and lightly doped, so most of the holes flow through the base to the collector. This creates a collector current that is proportional to the emitter current.

The amount of collector current that flows through the transistor can be controlled by the base current. A small base current can control a large collector current, which is why PNP transistors are used as amplifiers.

Applications of PNP transistors:

PNP transistors are used in a wide variety of electronic applications, including:

  • Amplifiers

  • Switches

  • Inverters

  • Voltage regulators

  • Oscillators

  • Digital logic circuits


One common example of a PNP transistor application is in a common emitter amplifier circuit. This circuit is used to amplify a voltage signal. The input signal is applied to the base of the transistor, and the amplified output signal is taken from the collector of the transistor.


PNP transistors are a versatile and powerful electronic device that is used in a wide variety of applications. By understanding the basic principles of operation of PNP transistors, you can design and build more complex and sophisticated electronic circuits.