Difference Between NPN And PNP Transistor

What Is NPN Transistor?

NPN is an acronym for Negative, Positive, Negative configuration. NPN transistor is a type of bipolar junction transistor which is composed of three layers, whereby two N-type doped semiconductor materials are separated by a thin layer of P-type doped semiconductor material.

In NPN transistor, the majority charge carriers are electrons whereas the minority charge carriers are holes. The NPN transistor has three terminals, which are Emitter, Base and Collector. The flow of electrons from Emitter to the collector constitutes current flow in the transistor.

The NPN transistor symbol shows an arrow pointing outwards from the Emitter to the Base which indicates the direction of the current flow. The working principle of a NPN transistor is such that when you increase current to the base terminal, then the transistor turns “ON” and it conducts fully from the collector to emitter. When you decrease the current to the base terminal, the transistor turns “ON” less and until the current is so slow, the transistor no longer conducts across the collector to emitter and shuts “OFF”.

Generally the NPN transistor is the most used type of bipolar transistors because the mobility of electrons is higher than the mobility of holes.

Application Of NPN Transistor

Mainly used in switching applications
Amplifying circuit applications
Used in applications where there is a need to sink a current.
Used in the Darlington pair circuits to amplify weak signals.

What You Need To Know About NPN Transistor

NPN is an acronym for Negative, Positive, Negative configuration.
In NPN transistor, the majority charge carriers are electrons whereas the minority charge carriers are holes.
NPN transistors are made up of two layers of P material with a sandwiched layer of N.
In NPN transistors, the current flows from the collector (C) to the Emitter (E).
In a NPN transistor, a positive voltage is given to the collector terminal to produce a current flow from the collector to the emitter.
The working principle of a NPN transistor is such that when you increase current to the base terminal, then the transistor turns ON and it conducts fully from the collector to emitter. When you decrease the current to the base terminal, the transistor turns ON less and until the current is so slow, the transistor no longer conducts across the collector to emitter and shuts OFF.
In NPN transistor, the emitter terminal’s arrow is pointing outwards.
In NPN electrons mobility is faster because NPN consists of electrons.
NPN has fast frequency response than PNP due to fast electron mobility.
The NPN transistor is powered ON where there is a positive (high) signal is applied at the base of NPN transistor. When the base of NPN is high, the current starts to flow from Collector terminal to Emitter terminal (C to E).
The ground signal of the NPN transistor at the base terminal is kept low to perform operations.
The switching time of NPN transistor is more as compared to PNP transistor because the majority charge carrier of PNP transistor is an electron.
The inside current in NPN transistor is because of the varying position of the electrons.
NPN transistor is commonly preferred for use because it has more electron mobility.

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What Is PNP Transistor?

PNP is an acronym for positive, Negative, Positive configuration. PNP transistor is a type of bipolar junction transistor which is composed of three layers, whereby two P-type doped semiconductor materials are separated by a thin layer of N-type doped semiconductor material.

In PNP transistor the majority charge carriers are holes whereas the minority charge carriers are electrons. Generally, these transistors have two PN junctions, that is Emitter–Base Junction and the Collector–Base junction. Normally, a positive voltage is given to the emitter terminal to produce current flow from the emitter to the collector. In other words, for a PNP transistor, the Emitter is more positive with respect to the Base and also with respect to the collector.

PNP transistor works when Base Emitter junction is forward biased and the Base Collector junction is reverse biased. The forward biased means that the P-terminal of the diode is connected to the positive of the supply and the n-type material is connected to the negative terminal of the supply. Reverse bias means that the negative region is connected to the positive terminal of the supply and p-region is connected to the positive terminal of the supply.

The PNP transistor symbol shows an arrow pointing inwards from the Emitter to the Base which indicates the direction of the current flow. A PNP transistor is considered “ON” when the source voltage connected to the base is low and turned “OFF” when it is high.

Application Of PNP Transistor

They are used as switches
Used in designing amplifier circuits such as Class-B amplifiers
Used in general motor control
Used in oscillators and modulators as amplifiers
Commonly used in Darlington pair circuits
Used in Radio-frequency circuits for wireless systems

What You Need To Know About NPN Transistor

PNP is an acronym for Positive, Negative, Positive.
In PNP transistor the majority charge carriers are holes whereas the minority charge carriers are electrons.
The PNP transistor is made up of two layers of N material with a sandwiched layer of P.
In a PNP transistor, the current flows from the Emitter (E) to the collector (C).
In a PNP transistor, a positive voltage is given to the emitter terminal to produce current flow from the emitter to the collector.
The working principle of a PNP transistor is such that when the current exists at the base terminal of the transistor, then the transistor shuts OFF. When there is no current at the base terminal of the PNP transistor, then the transistor turns ON.
In PNP transistor, the emitter terminal’s arrow is pointing inwards.
In PNP, electrons mobility is less because PNP consist of holes.
PNP has slow frequency response than NPN transistor.
A PNP transistor is turned ON when there is low signal applied to the base terminal. When the base of PNP transistor is at the low state (GROUND) the current starts to flow from Emitter to Collector (E to C).
In PNP transistor the ground signal at the base terminal is kept high to perform operations.
The switching time of PNP is less when compared to that of NPN.
In PNP transistor, the inside current is because of the varying position of the holes.
PNP is less preferred for use due to less electron mobility.

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