We explain what a transistor is, its origin and how it works. Also, the types of transistors and their integrated circuits.
What is a transistor?
It is called a transistor (from the English:transfer resystor, "Transfer resistor") to a type of semiconductor electronic device, capable of modifying an electrical output signal in response to an input signal, serving as an amplifier, switch, oscillator or rectifier thereof.
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 the need to control the flow of the electric current in various applications, as part of the evolution of the field of electronics. Its direct predecessor was an apparatus invented by Julius Edgar Lilienfeld in Canada in 1925, but it would not be until the middle of the century when it could be implemented using semiconductor materials (instead of vacuum tubes).
The first achievements in this regard consisted in 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, from 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 the 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 be able to withstand a certain amount of electrical voltage and a temperature resistance heating maximum.
How does a transistor work?
Transistors operate on a current flow, operating as amplifiers (receiving a weak signal and generating a strong one) or as switches (receiving a signal and cutting it off) of the same. This occurs depending on which of the three positions a transistor occupies at a certain moment, and which are:
- In active. A variable current level (more or less current) is allowed to pass through.
- Sectional. It does not let the electric current pass.
- In saturation. It allows all the flow of electric current to pass (maximum current).
In this sense, the transistor works like a stopcock in a pipe: if it is completely open, it lets in all the flow of the Water, if it is closed it does not let anything pass, and in its intermediate positions it lets more or less water pass.
Now, every transistor is made up of three elements: base, collector and emitter. The first is the one that mediates between the emitter (where the current flow enters) and the collector (where the current flow leaves). And it does so, in turn, activated by a lower electrical 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 by a certain amount; and if the base receives enough current, then the dam will open fully and the full modulated current will pass through.
It is thus understood that the transistor operates as a way of controlling the amount of electricity that happens at a certain moment, thus allowing the construction of logical relationships of interconnection.
Types of transistors
There are several types of transistors:
- Point contact transistor. Also called "contact tip", it is the oldest type of transistor and operates on a germanium base. It was a revolutionary invention, even though it was difficult to manufacture, brittle, and noisy. Today it is no longer used.
- Bipolar junction transistor. Manufactured on a crystal of semiconductor material, which is contaminated in a selective and controlled way with atoms of arsenic or phosphorus (donors of electrons), 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 positive voltage.
- Phototransistors. They are called this way to the sensitive transistors to the light, in spectra close to the visible. So that they can be operated by means of electromagnetic waves at a distance.
Integrated circuits
Integrated circuits are better known as chips or microchips, and they are small structures of silicon or other semiconductors, in an encapsulation plastic ceramic, which we usually find in the electronic panels of various devices (computers, calculators, televisions, etc.).
These circuits are made up of numerous tiny transistors and resistors placed on a sheet, to efficiently perform tasks of manipulating an electrical signal, such as the amplification.