A transistor is a type of semiconductor device that is used to switch or amplify electronic signals and power. It is a basic component of electronic circuits and is made from semiconductor materials, typically with three connections to an electronic circuit.
A transistor allows the regulation of electrical current through one set of terminals by applying a current or voltage to another set of terminals. The output power can be greater than the input power, making it useful for signal amplification. It can be packaged individually or as part of an integrated circuit. Transistors are widely used to amplify signals and power in electronic systems.
Invention of Transistor
In 1926, Julius Edgar Lilienfeld, a physicist from Austro-Hungarian, developed the theory of a field-effect transistor; however, it was not feasible to construct a functioning device at that time. The first operational transistor was the point-contact transistor, which was created by Walter Brattain and John Bardeen in 1947 at Bell Labs under the supervision of William Shockley. They were given the Nobel Prize in Physics in 1956 for their invention. Today, the metal-oxide-semiconductor field-effect transistor (MOSFET) is the most popularly used transistor. This technology was developed by Dawon Kahng and Mohamed Atalla in 1959 while they were working at Bell Labs. This technology has greatly impacted the industry of electronics, enabling the production of smaller, more affordable radios, calculators, computers and other similar devices.
A regular transistor consists of three layers of semiconductor materials, or terminals, which connect to an external circuit and allow the flow of current. The current flowing through one pair of terminals can be controlled by applying a voltage or current to another pair of terminals. In a circuit diagram, the circuit symbol changes according to its doping nature. A transistor has three terminals, namely:
- Base: This activates the transistor.
- Collector: This is the positive terminal of the transistor.
- Emitter: This is the negative terminal of the transistor.
The Revolutionary Role of Transistors in Modern Electronics
William Shockley, Walter Brattain and John Bardeen at Bell Telephone Laboratories in New Jersey were researching the characteristics of crystals such as germanium as a means of replacing the vacuum tubes utilised as mechanical relays in telecommunications. The vacuum tubes, which were utilised to boost sound and speech, were known to be power-hungry, produced heat, and required frequent replacement, resulting in high maintenance costs. The team at Bell Telephone Laboratories were nearing the end of their research without any breakthrough when they stumbled upon the invention of a “point-contact” transistor amplifier by using a purer material as a contact point. Their achievement was recognised with the Nobel Prize in Physics in 1956.
The invention of the transistor in the 1940s has led to significant progress in technology over the past 60 years. It replaced the bulky and power-hungry vacuum tubes in electronic devices such as televisions, radios, and other equipment. Its compactness, durability, and low power consumption have enabled miniaturisation, resulting in the creation of home computers, digital cameras, mobile phones and other electronic devices. Over the course of time, many variations of transistors have been developed, and they have their own electrical symbols and graphical representations. Research in the field of transistors is ongoing; therefore, we can expect electronic devices to continue to evolve and become more advanced in the future.
Below are the three important characteristics of transistors:
Properly configured, transistors can act as amplifiers. They work by taking in a weak input signal at the base junction, amplifying it and then releasing the stronger output signal through the collector. Most audio and other types of signal amplifiers use transistors.
Transistors are highly effective electronic switches, and their simplest use is as a switch. They can be utilised for a variety of switching operations, such as opening or closing a circuit. The way a transistor functions as a switch relies on its mode of operation, which typically involves using low-voltage DC to turn the circuit on or off. Transistors are also a fundamental component in digital computers, used for storing and processing data.
Transistor sizes can vary depending on the application, with some currently being made at the scale of billionths of a meter. This small size allows for a high density of transistors to be integrated into silicon chips, leading to the creation of compact electronic devices such as cell phones and other portable gadgets.
Advantages of Transistors over Vacuum Tubes
The key advantages of transistors that allowed them to replace vacuum tubes in most applications are:
- Their small size and weight result in smaller equipment.
- The lack of a cathode heater reduces power consumption, eliminates warm-up delay, and makes them immune to cathode poisoning and depletion.
- Low operating voltages that are compatible with small batteries.
- Greater energy efficiency in circuits, particularly for low-power applications.
- The availability of complementary devices provides design flexibility and allows for circuits such as complementary symmetry.
- The ability to manufacture large numbers of extremely small transistors as a single integrated circuit.
- Immunity to breakage, leakage, outgassing, and other physical damage.
High resistance to mechanical shock and vibration, providing physical ruggedness and reducing shock-induced spurious signals.