NPN vs PNP: Difference and Comparison

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.

Key Takeaways

  1. NPN transistors have one P-type material sandwiched between two N-type materials, while PNP transistors have one N-type material between two P-type materials.
  2. NPN transistors use electrons as the primary charge carriers, whereas PNP transistors use holes as the primary carriers.
  3. NPN transistors switch on when a positive voltage is applied to the base, whereas PNP transistors switch on when a negative voltage is applied to the base.


NPN is a type of transistor that has a single layer of P semi-conductors staying in between two layers of the N semi-conductor, and the emitter is N-doped. PNP is a type of transistor that has a single layer of N semi-conductor in two layers of P semi-conductor, and the emitter is P-doped.


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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. A 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. The N-type is called the emitter, and the collector is the P-type.

Comparison Table

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 the collector lead is known as an Emitter terminal. The three terminals on the transistor are called the 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 the 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 water, holes are like 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. The terminal switches off when the NPN current is reduced, but the current is present in the base in PNP.
  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.
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