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Transistor as a Switch

Last updated date: 28th Nov 2023
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A semiconductor device is a transistor used to amplify or switch electrical power and electronic signals. A semiconductor Transistor is composed of material usually whose least three terminals are connected to an external circuit. One pair of the transistor's terminals to whom a voltage or current applied to controls the current through another pair of terminals. Because the controlling (input) power can be lower than the controlled (output) power, a transistor can amplify a signal. Nowadays, many more transistors are found embedded in integrated circuits but some transistors are packaged individually.

Julius Edgar Lilienfeld an Austro-Hungarian physicist proposed the concept of a field-effect transistor in 1926, but it was not possible to actually construct a working device at that time. American physicists John Bardeen and Walter Brattain built The first working device was a point-contact transistor invented in 1947 while working under William Shockley at Bell Labs. For their achievements in physics, all three shared the 1956 Nobel Prize. MOSFET (metal-oxide-semiconductor field-effect transistor) is the most widely used transistor, also known as the MOS transistor, which was invented by Mohamed Atalla with Dawon Kahng at Bell Labs in 1959. The first truly compact transistor is the MOSFET that could be miniaturized and mass-produced for a wide range of uses.

The field of electronics was revolutionized by the paved and transistors, the way for smaller and cheaper radios, calculators, and computers, among other things. In the list of IEEE milestones in electronics is the first transistor and the MOSFET. The fundamental building block of modern electronic devices is the MOSFET, and is ubiquitous in modern electronic systems. Between 1960 and 2018 according to an estimate the total of 13 sextillion MOSFETs have been manufactured (at least 99.9% of all transistors), making the MOSFET the most widely manufactured device in history.


Practically in all modern electronics Transistors are the key active components. Thus many consider that the transistor is to be one of the greatest inventions of the 20th century.

In the most widely used transistor, used in applications ranging from computers and electronics to communications technology such as smartphones The MOSFET (metal-oxide-semiconductor field-effect transistor), also known as the MOS transistor, is by far. It is considered that the most important transistor is The MOSFET, possibly the most important invention in electronics, and the birth of modern electronics. Since the late 20th century the MOS transistor has been the fundamental building block of modern digital electronics, paving the way for the digital age. It is called a "groundbreaking invention that transformed life and culture around the world" by the US Patent and Trademark Office.

In a society like today transistors importance rests on the ability of the transistor to be mass-produced using a highly automated process which is semiconductor device fabrication that achieves astonishingly low per-transistor costs.

In 2009 an IEEE Milestone name was given after the invention of the first transistor at Bell Labs. IEEE Milestones also includes the list of inventions of the junction transistor in 1948 and the MOSFET in 1959.

Although over a billion individually packaged (known as discrete) MOS transistors every year are produced by several each company, along with diodes, resistors, capacitors and other electronic components, to produce complete electronic circuits, the vast majority of transistors are now produced in integrated circuits (often shortened to IC, microchips or simply chips). As of 2009, up to about twenty transistors consist of a logic gate whereas an advanced microprocessor can use as many as 3 billion transistors (MOSFETs).

In history the MOS transistor is the most widely manufactured device. Every day, billions of transistors are manufactured as of 2013, nearly all of which are MOSFET devices. An estimated total of 13 sextillion MOS transistors has been manufactured between 1960 and 2018, accounting for at least 99.9% of all transistors.

Transistor as a Switch

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The simplest application of the device is using a transistor as a switch. Either for opening or closing of a circuit, A transistor can be extensively used for switching operations. Behind the operation of a transistor as a switch the basic concept relies on its mode of operation. In this mode generally, the low voltage DC is turned off or on by transistors.

As switches both NPN and PNP transistors can be utilized. A signal amplifier can be handled differently from a basic terminal transistor by biasing both PNP and NPN bipolar transistors by an “OFF / ON” static switch.  solid-state switches are one of the main uses of the transistor to transform a DC signal “On” or “OFF”.

Including LEDs, Some devices, at the logical level only, require several milliamperes of DC voltages and can be directly controlled via the logical gate output. Generators, solenoids, or lamps like high power devices usually need more power to use transistor switches than the usual logic gate.

FAQs on Transistor as a Switch

Q1. Explain How a Transistor Acts as a Switch?

Ans: By a very small input current into a large output current, the transistors act as an amplifier. One the same hand it also acts as a switch. To base when there is no current little or no current flows between the collector and the emitter. So we can say that the base current switches the whole transistor off or on.

Q2. With a Transistor Why is a Relay Used?

Ans: Transistor and relay are most often used for this purpose. A relay is the switch that is controlled by a very small electric current. Relays are advantaged of the fact that when we pass electric current through the wire a magnetic field is generated surrounding the wire this is called induction.

Q3. Transistors Which Region Acts as an Open Circuit.

Ans: There are regions which tend to be considered as the open circuit. The collectors have an effect on the transistor and base being opened. The emitter and collector and base current are all zero in this mode of operation.

Q4. Why are Transistors Used as Switches?

Ans: Transistors one of the common usage is that it tends to behave as an open circuit. A transistor conducts current across the emitter-collector path only when a voltage is applied to the base. The switch is off when no voltage is applied. When the voltage base is present the switch is on.