PNP Transistor – Definition, Working, Symbol, Types, Uses & Characteristics

Define PNP Transistor?

What is PNP Transistor?

At the point when a single n-type semiconductor layer is sandwiched between two p-type semiconductor layers, a PNP Transistor is formed.

The circuit image/symbol and diode analogy of PNP Transistor is displayed in the below figure.

PNP Transistor development or Constructions

The PNP Transistor is comprised of three semiconductor layers: one n-type semiconductor layer and two p-type semiconductor layers.

The n-type semiconductor layer is sandwiched between two p-type semiconductor layers.

The PNP Transistor has three terminals: emitter, base and collector. The emitter terminal is associated with the left side p-type layer. The collector terminal is associated with the right side p-type layer. The base terminal is associated with the n-type layer.

The PNP Transistor has two p-n junctions. One junction is shaped between the emitter and the base. This junction is called emitter base junction or emitter junction. The other junction is shaped between the base and the collector. This junction is called gatherer base junction or collector junction.

Working of a PNP Transistor
Unbiased PNP Transistor

Whenever no voltage is applied to a pnp transistor, it is supposed to be an unbiased pnp transistor. At the left side p-region (emitter) and right side p-region (collector), holes are the larger part carriers and free electrons are the minority carriers while in n-region (base), free electrons are the greater part carriers and holes are the minority carriers.

We realize that the charge carriers (free electrons and holes) consistently attempt to move from higher concentration region to the lower concentration region.

For holes, p-region is the higher concentration region and n-region is the lower concentration region. Also, with the expectation of free electrons, n-region is the higher concentration region and p-region is the lower concentration region.

Therefore, the holes at the left side p-region (emitter) and right side p-region (collector) experience a repulsive power or force from one another. Accordingly, the holes at the left side and right side p-regions (emitter and collector) will move into the n-region (base).

During this interaction, the holes meet the free electrons in the n-region (base) and recombines with them. Subsequently, depletion region (positive and negative ions) is framed at the emitter to base junction and base to collector junction.

At emitter to base junction, the depletion region is entered more towards the base side, comparatively; at base to collector junction, the depletion region is entered more towards the base side.

This is on the grounds that at emitter to base junction, the emitter is intensely doped and base is lightly doped so the depletion region is infiltrated more towards the base side and less towards the emitter side. Similarly, at base to collector junction, the collector is heavily doped and base is daintily doped so the depletion region is entered more towards the base side and less towards the collector side.

The collector region is softly doped than the emitter region, so the depletion layer width at the collector side is more than the depletion layer width at emitter side.

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