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BASIC KNOWLEDGE - TRANSISTOR Transistors: the building blocks of modern electronics

Updated on 04.08.2022 From Erika Granath

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Transistors have ushered in a revolution in the electronics industry and utterly changed the way technology and society functions. The current generation of transis-tors are so small that billions of these devices can fit onto a single computer chip.

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.
A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.
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What is a transistor?

Transistor Definition

Transistors are simple three-terminal semiconductor devices made of silicon or germanium that can be thought of as the “brain cells” of electronic devices. Like neurons in the brain that communicate with other cells to transfer nerve impulses, transistors are designed to either a) take an electric current and amplify it to produce a larger current, or b) work as a switch that connects or disconnects an electrical circuit’s conducting path.

Most transistors are made of silicon due to its abundance and excellent properties as a semiconductor, with modern variants measuring just a few nano-meters in width. Various transistors have been developed over the past 70 years, with the bipolar junction transistor (BJT) and metal-oxide-semiconductor field-effect transistor (MOSFET) being the most widely used types today.

How does a transistor work?

Transistors are made of a semiconductor materials (silicon or germanium) with three terminals that allow for an electric current to be amplified and prevent or allow the flow of current from one transistor to the next. When a weak voltage or current is applied to one of the terminals (the input), the transistor enables the charge to flow towards or away from the other two terminals, which amplifies it by the time it reaches the output. This charge is then transferred from the output circuit to the rest of the system. When used as a switch, the transistor uses the small input charge to interrupt or divert the larger charge. This is how the zeros and ones in binary code are created: the presence or absence of an electrical charge will close or open the switch, with the resulting output being categorized as a 1 or a 0. This code is used by computers to store data and perform calculations.

Advantages of transistors

The reasons for using transistors are numerous, especially since the advent of MOSFET semiconductor devices in the early 1960s, the commercialization of which led to the meteoric rise of the consumer electronics industry. The advantages of transistors include the fact that:

  • At just a few nano-meters in size, they require very little space (especially when embedded in an integrated circuit)
  • Only a very low supply voltage is required for operation
  • There’s minimal risk of overheating
  • Transistors are mechanically strong due to being a solid-state circuit

Overview of transistor types

The following chapters go into more detail about the various types of transistor used in the field of electronics today. A brief overview is provided below:

  • Bipolar junction transistor (BJT): works as an amplifier and a switch, commonly produced in the millions for a single electronic device
  • Field-effect and junction field-effect transistor (FET/JFET): switch, amplifier and resistor that exclusively uses voltage to function
  • Metal-oxide-semiconductor field-effect transistor (MOSFET): insulated-gate transistor where the voltage determines a device’s conductivity
  • Thyristor: a special type of transistor consisting of p-type and n-type semiconductor layers, functions exclusively as a switch

Common uses of transistors in the world today

The transistor’s importance to society is evident from its inclusion in the Institute of Electrical and Electronics Engineers’ list of historical achievements in the field of electronics. Found in everything from games consoles to modems to wearable technology, transistors are everywhere⁠—and in huge numbers. A standard smartphone, for example, will contain billions of transistors distributed across its CPU, GPU, memory, storage and peripheral units, all working as part of integrated circuits to amplify and switch electronic signals. A home computer will contain many more on top of that, while the radiation-hardened transistors embedded in satellite and aerospace applications are, when taken together, too numerous to count.

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