Difference Between NPN and PNP

A transistor is a semiconductor device. Power and electronic signals can be amplified by the transistor. John Bardeen, Walter Brattain, and William Shockley developed transistors. This was curated at Bell Labs in 1947.

The first model of the transistor was made by using point-contact germanium.


The main difference between NPN and PNP is NPN has one layer of p semiconductor between two layers of n semiconductor, but PNP has one layer of n semiconductor between two layers of p semiconductor. The acronym is for NPN is negative-positive negative, but The acronym for PNP is positive negative positive. The emitter is n doped in NPN, but the emitter is p doped in PNP.


The NPN transistor has three terminals: collector, base, and emitter. The collector is grounded while the base and emitter are positioned to either increase or decrease current flow through the transistor.

A bipolar junction transistor (BJT) is a type of transistor that is manufactured using two types of semiconductors, either n-type and p-type silicon or germanium.

The PNP transistor is a type of transistor. PNP transistor is also known as a bipolar junction transistor or BJT. A bipolar junction transistor (BJT) is an amplifier or switch. It is a three-layer transistor.

The PNP version contains two layers of doped silicon and one layer of intrinsic silicon between the N-type. N-type is called the emitter, and the collector is P-type.

Comparison Table Between NPN and PNP

Parameters of ComparisonNPNPNP
StructureTwo N layers and one P-layerTwo P-layers and one N layer
Flow of currentbase to emitteremitter to base
Reduced currentterminal switches offcurrent in the base
Full formNegative Positive NegativePositive Negative Positive
Positive voltageCollectorEmitter

What is NPN?

NPN transistor is a device that can be used to amplify current and voltage signals. In this article, we will discuss the working of an NPN transistor, the symbols used for it, and how it works in real life.

The team later replaced it with a silicon-based alternative because it produced better results. This NPN transistor has three terminals. They are emitter, collector, and base.

When voltage is applied across the B and C terminals, current will flow between the E and C terminals according to the characteristics.

NPN (negative-positive-negative) transistor is a three-lead semiconductor device that is used for amplification and switching applications.

It is made up of two P-type semiconductors and one N-type semiconductor, arranged in the PNP junction configuration.

It can be considered as a voltage amplifier or current amplifier depending on the biasing arrangement of the input and output leads.

The emitter lead is commonly called a base terminal, while collector lead is known as an Emitter terminal. The three terminals on the transistor are called emitter, base, and collector.

It was developed to help solve this problem by allowing for more complex logic functions with fewer transistors than the diode OR gate previously used.

The NPN did not replace the diode OR gate but allowed manufacturers to use less expensive germanium transistors in place of more expensive silicon transistors while still creating all-transistor logic circuits.

What is PNP?

A PNP transistor consists of two P-type, which are separated by one layer of N-type. The thickness and doping levels of the base layer determine the current flow between emitter and collector regions.

The basic operation of a hypothetical bipolar junction transistor (BJT) can be understood with an analogy to water flowing through a pipe.

In this example, electrons are like the water, holes are like the pipes, and an electric field is similar to the pressure difference between two ends.

The p-n junction diode is used in nearly all solar cells to absorb light across the entire visible spectrum.

When light strikes this device, electrons are knocked loose from their atoms, creating free mobile charge carriers (electrons). These mobile charge carriers can then flow freely through the material.

A PNP transistor has three terminals. The power NPN BJT is the more common type, but PNP transistors are used in some applications due to various advantages.

A PNP transistor is a type of transistor used in amplifier circuits and oscillator circuits. A PNP transistor consists of a collector, base, and emitter.

Main Differences Between NPN and PNP

  1. NPN has one p semiconductor between two n semiconductors, but PNP has one n semiconductor between two p semiconductors.
  2. Current from base to emitter, but PNP current flows from emitter to base.
  3. The emitter is N-doped in NPN, but the emitter is P-doped in PNP.
  4. Terminal switches off when NPN current is reduced, but in PNP, the current is present in the base.
  5. The acronym of NPN is Negative Positive Negative, and for PNP is Positive Negative Positive.
  6. Positive voltage to a collector in NPN but emitter in PNP.


The PNP transistor is made by using two NPN transistors connected back to back, or what is commonly called a ‘PNP stack.’

The PNP transistor has a positive voltage applied at its emitter terminal, and this voltage is passed through to the base terminal through a resistor.

This positive voltage turns off the BN junction so that there will be no conduction. PNP transistor or P-N-P Transistor is a three-terminal semiconductor device that has been widely used in many electronic devices.

It is also called BJT (Bipolar Junction Transistor), and it was invented by William Shockley, working for Bell Laboratories, New Jersey.

The NPN transistor is a type of bipolar junction transistor that is widely used in modern electronics.

It is an enhancement mode device, which means that it amplifies signals by using both positive and negative feedback to swing the input signal between the collector and emitter terminals.

The name of this device depends on the emitter, collector, and base. A diode is considered at the base region connected in reverse bias between emitter and collector regions.


  1. https://ieeexplore.ieee.org/abstract/document/1486465/
  2. https://ieeexplore.ieee.org/abstract/document/1476220/
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