Types of Transistor Classified : You May Not Know

Different Types of transistor and their working principle and applications

Types of transistor

Types of transistor

This piece of writing offers an overview of a transistor, different types of transistor along with its applications. In the world of electronics and communications, transistor is one of the most popular semiconductor devices generally used for amplifying signals. In addition to this, transistors are also used in electrical boards for switching circuits. A general purpose transistor is manufactured by using solid material. Base (B), Emitter (E) and the collector (C) are three main components of a transistors that can be further connected with the other components inside the circuit. In few transistors, you will also find fourth component, i.e. substrate (S). On any electrical circuit or board, a transistor is the most active component.

A transistor is the basic unit or component of any modern electronic device right from large industrial machines to pocket sized mobile phones. Invention of transistors revolutionized the stream of electronics and become a boon for cheaper as well as smaller computers, radios, fm transmitters calculators, mobile phones including several other things.

The transistor’s tractability, low cost, as well as consistency have made it a universal component. Circuits made of transistor have easily replaced electro-mechanical components used in manufacturing controlling appliances and other machinery. With the introduction of transistor, it is often cheaper as well as easier to use a standard microcontroller and write a computer program to carry out a control function than to design an equivalent mechanical system to control that same function.

While using transistor as the amplifier, you can use them in high as well as low level, oscillators, modulators, frequency stages, detectors besides in any circuit. In digital circuits they can be used as switches. In this world, there are large number of manufacturers who makes semiconductors (transistor is a member of this family of device) of hundreds of different types. There are high, medium and low power transistors, for running with high in addition to low frequencies, for working with very high voltages and or high current. On the basis of design, structure and functionality, transistors are classified into below given following categories.

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NPN Transistor

It is one of the most popular among the two main types of transistor. This NPN-type transistor contains two n-type semiconductor materials which were divided by a very thin layer of p-type semiconductor. In NPN transistor, electrons are majority charge carriers whereas holes are the smaller charge carriers. Due to the higher flow of electrons then holes, NPN transistor is widely used bipolar transistor.

PNP transistors

It is the second type of bipolar junction transistor. It contains two p-kind semiconductor substances which were divided by a thin coating of n-kind semiconductor. The working of PNP transistors is opposite of the working of NPN transistors. Here, the majority charge carriers are holes and minority charge carriers are electrons. A PNP transistor in in ‘ON’ state when the base terminal is dragged to ‘LOW’ with respect to emitter.

Junction transistors

Junction transistors

Junction transistors

This type of transistors is also known as Bipolar Junction Transistor (BJT). Junction transistors consists three known terminals, i.e. collector (C), base (B) and emitter (E). This kind of transistor forms a junction or joining point amid p-type as well as n-type semiconductors. On the basis of construction, junction transistors are further divided into two transistors types- NPN and PNP transistors. Sometimes, BJT or junction transistors are also considered as current controlled devices. Generally, bipolar junction transistors worked in three most popular areas which are listed below-

  • Saturation area- in this area, the BJT is in completely ‘ON’ phase and act as a closed switch.
  • Active area- in this area, BJT works as an amplifier.
  • Cut-off area- in this area, the BJT is in ‘OFF’ condition and hence flow of current through the transistor will be zero.

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Field Effect Transistor

Field Effect Transistor

Field Effect Transistor

Field effect transistor or FET is made up of 3 components a source (S), a drain (D) and a gate (G). This type of transistor is also known as considered as Voltage-control devices. Field effect transistors are further classified into two types- insulated gate FET (IG-FET) and JFET (junction field effect transistors). IG-FET is also known as MOSFET transistors. There is also consideration of fourth region which is known as substrate or base in order to establish connection throughout the circuit. Field Effect Transistors have full control over the shape as well as the size of a channel equipped amid source and drain which would produce by the applied voltage.

Most of the FETs are uni-polar transistors since they work on the single channel operation principle. Moreover, FETs also have high current gain as compare to BJTs. Due to which, FETs are able to draw a little amount of current from a circuit’s power supply which is also an advantage of FETs over BJTs. Therefore, FETs don’t disturb the original circuit’s voltage components to which it is joined. FETs are much better than BJTs since they are cheaper, easy to manufacture and most importantly, require very less amount of voltage in loading.

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Hetero Junction Bipolar Transistor (HBT)

HBTs are used in both analog as well digital microwave applications where use of high frequency bands are common. HBTs are manufactured by combining collector-to-substrate as well as reduced base resistance. Due to which, HBTs are able to supply much faster switching speeds than other transistors like silicon bipolar transistor etc. The processing of HBT needs very less lithography. Due to high powered-added efficiency, good linearity and low phase noise, HBTs can be easily used in both high-reliable as well as profitable applications like laser devices, mobile telephones, power amplifiers etc.

Types of transistor based on working or function

On the basis of functions, transistors are also classified into below given following categories.

Small signal Transistors

This type of transistor is used for switching purposes and their basic function is to amplify very small signals. This type of transistors comes in both form i.e. NPN and PNP transistors. Every small signal transistors hold some hFE value. On the basis of that hFE value, you can understand the power of transistor of amplifying the signal. This type of transistors were generally used in all types of electronic devices as well as digital circuit’s applications. Some small signal transistors were used only for ‘ON’ and ‘OFF’. Examples of few circuits where small signal transistors are commonly used- timer circuits, relay driver, LED diode driver, infrared diode amplifier, audio mute function, bias supply circuits and so on.

Small switching transistors

The primary use of this type of transistor is switching. Further, they can also be used for amplification. Small switching transistors are also comes in both NPN and PNP transistors forms. The hEF value of small switching transistors lies in between 10 to 200.

Other types of transistors

Apart from above mentioned types of transistors, there are several other types of transistors available in the market like power transistor, high frequency transistor, photo transistor, uni-junction transistor, Schottky transistor, multiple-emitter transistor, dual-gate transistor, diffusion transistor, avalanche transistor etc.

Do share your thought about or you may ask any doubt in the comment below.

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Types of Transistors and their applications [Explained]
Article Name
Types of Transistors and their applications [Explained]
In this article the overview of a transistor, different types of transistors along with its applications and explained in detail.
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EEE Projects
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This article has 4 comments

  1. James Barbus Reply

    Hi, i’m working on 12v 10A projects, which transistor am i suppose to use ?


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