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 English: transfer resistor“transfer resistor”) to a type of semiconductor electronic device capable of modifying an output electrical signal in response to an input one, 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 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, but it would not be until mid-century when it could be implemented using semiconductor materials (instead of vacuum tubes).
The first achievements in this sense consisted of expanding the power of an electrical signal by conducting it through two gold struts applied to a germanium crystal.
The name transistor 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 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.
In the construction of transistors today, materials such as germanium (Ge), silicon (Si), gallium arsenide (GaAs) or alloys of silicon and germanium or silicon and aluminum are used. Depending on the material used, the device will be able to withstand a certain amount of electrical voltage and a maximum resistance heating temperature.
How does a transistor work?
The 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). This occurs depending on which of the three positions a transistor occupies at a given moment, which are:
- Active A variable current level (more or less current) is allowed to pass.
- Sectional It does not allow electric current to pass.
- In saturation It allows the full flow of electric current to pass (maximum current).
In this sense, the transistor works like a stopcock of a pipe: if it is completely open it allows the entire flow of water to enter, if it is closed it does not allow anything to pass through, and in its intermediate positions it allows 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 (where the current flow enters) and the collector (where 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 placed 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 completely and the entire modulated current will pass through.
It is thus understood that the transistor operates as a way of control the amount of electricity that happens at a certain moment, thus allowing the construction of logical interconnection relationships.
Types of transistors
There are various 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, fragile 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 manner with arsenic or phosphorus atoms (electron donors), to generate the base, emitter and collector regions.
- Field effect transistor In this case, a silicon bar or some other similar semiconductor is used, on whose terminals ohmic terminals are established, thus operating by positive voltage.
- Phototransistors Transistors sensitive to light, in spectrums close to the visible, are called this. So they can be operated by means of electromagnetic waves at a distance.
integrated circuits
Integrated circuits are better known as chips or microchips, and are small structures made of silicon or other semiconductors in a ceramic plastic encapsulation, which we usually find in the electronic panels of various devices (computers, calculators, televisions, etc.).
These circuits are made up of numerous transistors and resistors tiny placed on a sheet, to efficiently carry out tasks of manipulating an electrical signal, such as amplification.
