What is a transistor?
A transistor is a kind of semiconductor device that is short for transfer resistance regulates or controls the electrical signal like current or voltage. On 23 December 1947, it is developed by three American physicists William Shockley, Walter Brattain, and John Bardeen. Generally, it is a switching device or miniature device used to transfer a weak signal from a short resistance circuit to a high resistance circuit. It is a component that is made up of semiconductors. The below picture represents the example of a transistor.
In most electronic devices, the transistor is one of the key components, and it generates the binary bits 0's and 1's that are used by the computer to establish communication as well as deal with Boolean logic. In the history of science, one of the most important inventions is considered the transistor that forms logic gates when placed in different configurations. Those gates combine into full adders or into arrays known as half adders. Two PN diodes are included in the transistor, which is linked back to back.
A transistor consists of three terminals: input, output, and controlling switching. The name of the three terminals contained by the transistor is the emitter, base, and collector.
These terminal names are specified on the basis of the common terminal of the transistor. It is widely embedded into integrated circuits or found in circuit boards as discrete parts. For modern electronic devices, it is the important structure block. Doping, a chemical process used to create transistors, in which an extra positive charge (P-type) or extra negative charge (N-type) is gained by the semiconductive material. The PNP or NPN are two configurations for this, with middle material that function as the base or flow control. Through the whole component, a large amount of electricity flowing when a little change in the voltage or current in the middle base layer, which can be led to use as an amplifier.
Parts of the Transistor
A transistor is made by more specifically terminals or three layers of semiconductor materials, which led to carry the current and establish a connection to an external circuit. With the help of other pairs of terminals, a current is controlled by the voltage. A transistor has three terminals, which are as follows:
The NPN transistor and PNP transistor are the two kinds of a transistor. Equally, the transistor that has two layers of P-type material and one layer of N-type material is called as a PNP transistor. The below picture is representing the symbol of NPN and PNP transistor. The arrow symbol describes the flow of emitter current with forward biasing, which is implemented to the emitter-base junction. The route of the current is the primary difference between the PNP and NPN transistors.
In the NPN connection, the conventional current flows out of the emitter, as specified with the help of the outgoing arrow in the figure. Similarly, in the PNP connection, the conventional current flows into the emitter; it can be seen in the figure, which has represented by the inward arrow.
Types of Transistors
Transistors are mainly two types on the basis of how they are used in a circuit, which are as follows:
Bipolar Junction Transistor (BJT)
Bipolar Junction Transistors are the kinds of transistors that comprise of terminals, base, emitter, and collector. It is considered a current-controlled device. A much larger current flow between the collector and emitter terminal can be controlled by a minor current entering the base region of the transistor. Moreover, BJT (Bipolar Junction Transistor) has other two major types, PNP transistor, and NPN transistor, which are discussed below:
Field Effect Transistor
The three terminals, Gate, Source, and Drain, are used to make up Field Effect Transistors (FET). These kinds of transistors are considered voltage-controlled devices. The gate terminal controls the current between source and drain. The P channel FET or N channel FET in this transistor are used for conduction.
The value of the impedance of the circuit inversely affects the current, according to ohm's law. That means the current is very low if the impedance is high. Thus, from a circuit's power source, FETs draw very little current. The below image is of the Field Effect Transistor.
Therefore, the original circuit power elements that are connected to transistors are not disturbed by the transistors. As compared to bipolar transistors, FETs do not offer the high amplification that is the main limitation of FET.
FETs offer advantages, such as they cause less loading, easier to manufacture, and cheaper in cost. However, bipolar transistors are better in terms that they offer greater amplification. JFETs and MOSFETs are the main types of Field Effect Transistors (FET). Although MOSFETs and JFETs are very close to each other, MOSFETs have higher input impedance values as compared to JFETs. FET includes some features, which are discussed below:
Some difference between FET and BJT
Working of Transistor
Usually, transistors are made of silicon as it has greater current, high voltage rating, and less temperature sensitivity. The base current is established by the emitter-base section kept in forward biased, which moves via the base region. The base current has a very small magnitude. The base current is responsible to make a hole in the base region or electrons to transfer into the collector region.
As compared to the emitter, transistors have a smaller number of electrons as the base of the transistor is lightly doped and very thin. The emitter's few electrons are moved towards the collector region. Therefore, it can be said that by varying the base region, the large collector current is obtained.
The crucial component of an electronic device is a transistor that controls the electrical signal like current or voltage. Although a vacuum tube was developed by eccentric American inventor Lee De Forest in 1906, it used a lot of electrical power, and it was bulky in size. Also, the transistor was an appropriate solution to work with electronics as it uses much less power and small in size as compared to vacuum tubes.
During the war, the team had made radar possible by using some of the advances in semiconductor research.
On 23 December 1947, the transistor was developed by three American physicists William Shockley, Walter Brattain, and John Bardeen, and successfully demonstrated at Bell Laboratories in Murray Hill, New Jersey. However, as compared to the two others, William Shockley played an important or much different role in the development process of the transistor. For more than ten years, Shockley had been working on this type of project. Although he had the ability to work out the theory successfully, he could be unable to construct a working model after practicing for eight years.
To handle the engineering and development, Bardeen and Brattain were called. And they created the "point-contact" transistor. But the bipolar transistor was designed by Shockley that replaced the point-contact" transistor, and it was superior to it. Therefore, Shockley had a large part in the invention of the transistor. William Shockley went to work for Bell Labs as he completed his doctorate, specializing in quantum physics. In 1936, he had begun working on the basis for the transistor, the solid-state physics theory. A fine wire was included in signal detectors contained by early radios, which impinged on a galena crystal. This fine wire was known as a cat's whisker. However, these early radios were unable to work successively. But it was the basis for the "point-contact" transistor, the principle on which the crystal detector worked.
In the first transistor, rather than galena, Brattain and Bardeen used germanium. However, they used similar cat whiskers. The bipolar transistor designed by Shockley eliminated the troublesome point contacts
In 1954, the commercial production of junction transistors for portable radios begun for the first time by the Texas Instruments of Dallas. In the same year,1954, there was an announcement by IBM that it was planning to replace vacuum tubes with transistors from its computers and introduced its first computer that had 2000 transistors. The production of transistors was also started by the Sony Company of Japan that dominated the market. Instead of vacuum tubes, Sony started to produce television sets with the help of using transistors in the 1960s. And, transistors replaced vacuum tubes, and almost vacuum tube technology became obsolete. As of 2016, more than seven billion transistors can be included by the most powerful computer processor.
Advantages and Disadvantages of the transistors
The below table contains the benefits and drawbacks of a transistor.