Transistor Concept, Types And How It Works


What is a transistor?

Transistor is called (in English:  transfer resistor, “resistor transfer”) to a type of electronic semiconductor device, capable of changing an electrical output signal in response to an input, serving as an amplifier, oscillator or rectifier Of the same.

It is a type of device commonly used in many devices, such as watches, lamps, tomographs, cell phones, radios, televisions, and, above all, as a component of integrated circuits (chips or microchips).

Transistors have their origin in need to control the flow of electric current in various applications, as part of the evolution of the field of electronics. Its direct predecessor was a device invented by Julius Edgar Lilienfeld in Canada in 1925. Still, it would not be until the middle of the century when it could be implemented using semiconductor materials (instead of vacuum tubes).

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The first achievements in this regard consisted of expanding the power of an electrical signal by conducting it through two gold struts applied to a germanium crystal.

The transistor name was proposed by the American engineer John R. Pierce, based on the first models designed by Bell Laboratories. The first contact transistor appeared in Germany in 1948, while the first high-frequency transistor was invented in 1953 in the United States.

These were the first steps towards the electronic explosion of the second half of the 20th century, which allowed, among many other things, the development of computers.

Materials such as germanium (Ge), silicon (Si), gallium arsenide (GaAs), or alloys of silicon and germanium or silicon and aluminum are used in the construction of transistors today. Depending on the material used, the device will withstand a certain amount of electrical voltage and a maximum resistance heating temperature.

How does a transistor work?

Transistors operate on current flow, operating as amplifiers (receiving a weak signal and generating a strong one) or switches (receiving a signal and cutting off the flow ). This occurs depending on which of the three positions a transistor occupies at a given moment, and which are:

  • Active. The passage of a variable current level (more or less current) is allowed.
  • Sectional. It does not let the electric current pass.
  • In saturation. Let all the electric current flow through (maximum current). 

In this sense, the transistor works as a stopcock for a pipeline: if it is fully open, it allows the ent.If the flow of water to enter, if it is closed, it does not allow a.Ifng to pass, and in its intermediate positions, it.In more or less water to pass through. Now, every transistor is made up of 

Three elements: base, collector, and emitter. The first is the one that mediates between the emitter (through which the current flow enters) and the collector (through which the current flow leaves). And it does so, in turn, activated by a smaller electric current, different from that modulated by the transistor.

In this way, if the base does not receive current, the transistor is located in the cut-off position; if it receives an intermediate current, the base will open the flow in a certain amount; and if the base receives sufficient current, then the dam will be fully opened, and the total modulated current will pass.

Thus it is understood that the transistor operates as a way to control the amount of electricity that passes at a certain moment, thus allowing the construction of logical interconnection relationships.

Types of transistors

There are different types of transistors:

  • Point contact transistor.  Also called “contact point,” it is the oldest type of transistor and operates on a germanium base. It was a revolutionary invention, despite being difficult to manufacture, fragile and noisy. Today it is not used.
  • Bipolar junction transistor. Manufactured on a crystal of semiconductor material, which is selectively and controlled contaminated with arsenic or phosphorus atoms ( electron donors ), thus generating the base, emitter, and collector regions.
  • Field-effect transistor. In this case, a silicon bar or some other similar semiconductor is used, in whose terminals ohmic terminals are established, thus operating by a positive voltage.
  • Phototransistors. Transistors sensitive to light are called this way, in spectra close to the visible one. So they can be operated by electromagnetic waves at a distance.

Integrated circuits

Integrated circuits are better known as chips or microchips. They are small structures of silicon or other semiconductors, in a ceramic plastic encapsulation, that we usually find in electronic panels of various devices (computers, calculators, televisions, etc.).

These circuits are made up of numerous tiny transistors and resistors placed on a foil to efficiently perform tasks of manipulating an electrical signal, such as amplification.

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