What is a transistor?

A transistor is a kind of device that is responsible for regulating the flow of current that circulates through a circuit, thus acting as a kind of amplifier or switch for both electrical and electronic signals.

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In this sense, a transistor is a kind of electronic type device considered as a semiconductor that has the sufficient capacity to modify a certain electrical output signal, acting in response to an input, thus serving as a switch, amplifier or rectifier of it.

This device is commonly used in electrical and electronic devices such as cell phones, radios, lamps, watches, among other integrated circuit components , such as those with chips or microchips.


The transistor was invented in 1951 , being the most impressive electronic component of the moment, initiating a new era in electronic devices, surpassing any expectation or vision of the moment. It is also known as a bipolar or electronic transistor.

It is an electronic component developed by semiconductor elements, commonly used, as we find it current in various everyday devices such as radios, alarms, cars, computers, etc.

They come to replace the old thermionic keys of a few decades ago. Thanks to them, it was possible to manufacture portable radio receivers commonly called “transistors”, televisions that turned on in a couple of seconds, color televisions, and so on.

Before the transistors came to light, the tube devices had to deal with quite high voltages , they waited more than 30 seconds to be able to start working, and in no case could they operate on batteries due to the high consumption they had.

How does it work

These devices work on a certain flow of current, operating either as switches or amplifiers. This function applies, depending on which of the three functions you are executing, namely:

  • Active: allows variable flow of certain current level.
  • Cut: does not let any type of current flow.
  • Saturation: allows the electric current to pass in its entirety.

It is important to note that the function of a transistor is just as the function of a pipe stopcock, that is, if it is open it lets the water pass completely, if it is closed, it does not let anything through and if it is in a medium stage , the water flows in greater or lesser quantity.

Types of transistors

There are various types of transistors that exist, among them we can find:

  • Point contact : they are also known as contact point. It is one of the oldest types of transistor and works on a germanium base.
  • Bipolar junction : it is manufactured on a crystal that functions as a semiconductor material, this device is selectively contaminated and is controlled with atoms composed of arsenic and phosphorus.
  • Field effect: in this transistor a silicon bar is used as a semiconductor or other similar material and ohmic terminals are placed on its terminals, operating in this way through the positive voltage.
  • Phototransistors: they are light-sensitive transistors, operating through electromagnetic waves at a distance.

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