Different transistor types and their uses

Transistors can be found in different electronic circuits. They’re made through semiconductors and they’re crucial for turning a current on and off, acting as a gateway for the current to flow through. While they seem to be a relatively small component, they have, since their inception, been key in changing how electronic devices function. 

There are different types of transistors, and these have specific functions in a range of applications. Here, we look at how transistors work, where they’re used and why they’re so important. 

What is a transistor?

The first transistor was invented in 1947 at Bell Laboratories in New Jersey. What started as a relatively small demonstration after a decade of research soon snowballed, quickly being dubbed the most important invention of the 20th century. 

The transistor – also known as the point-contact transistor – is a semiconductor device that’s used to either amplify or switch electrical signals. When it was first introduced in the late 1940s, the goal was to replace mechanical relays and the vacuum tubes commonly found on TV sets and other devices at the time. 

A standard transistor comprises three layers of semiconductor materials – or terminals – that carry the current and connect to an external circuit. The three terminals for a transistor are the base, which triggers the transistor; the emitter, which is the negative lead; and the collector, which is the positive lead.

Common transistor types

Different applications call for certain types of transistors to be used. There are three popular transistor types: 

  • BJT transistors: These are three-pin devices made from three layers of silicon that are used to amplify the current collected to a higher emitted current. There are different types of BJT transistors. PNP transistors tend to be used in place of NPN transistors and the two are opposites despite both being a type of BJT. 
  • JFET transistors: Junction field effect transistors are used as resistors, amplifiers and switches. 
  • MOSFET transistors: Metal oxide semiconductor field effect transistors – or MOSFET – are the most popular type of transistor. These are widely used for switching applications and power circuits. They’re found in a wide range of applications and available in depletion and enhancement types, meaning they can be used to decrease or increase current. 

Transistor applications 

Even basic computer applications require transistors in order to operate. In fact, there’s a reason why transistors are considered the most important electronic invention of the 20th century. 

This relatively small component is the building block for many electrical devices that we use today, from calculators and cameras to computer memory chips and pacemakers. They’ve literally helped save lives and without them, we wouldn’t have the laptops we work from and the tech we use every day. 

Will Fastiggi
Will Fastiggi

Originally from England, Will is an Upper Primary Coordinator now living in Brazil. He is passionate about making the most of technology to enrich the education of students.

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