transistor

transistor
Name	Transistor
Caption	A selection of modern transistors in various packages.
Type	Active component
Invented	John Bardeen, Walter Brattain, William Shockley
First produced	1947
Pin count	3 (typically)

transistor. A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is the fundamental building block of modern electronic devices, constructed from semiconductor material with at least three terminals for connection to an external circuit. By applying a voltage or current to one pair of terminals, the current through another pair is controlled, allowing it amplify a signal, act as a switch, or regulate voltage. Its invention at Bell Labs revolutionized the field of electronics, leading to the replacement of bulky, fragile, and power-hungry vacuum tubes and enabling the microprocessor and digital revolution.

History

The transistor effect was first successfully demonstrated on December 16, 1947, by the team of John Bardeen, Walter Brattain, and William Shockley at Bell Labs in Murray Hill, New Jersey. This first point-contact device was followed shortly by Shockley's superior bipolar junction transistor design. The trio was awarded the Nobel Prize in Physics in 1956 for their work. Early commercial production was led by companies like Texas Instruments and Fairchild Semiconductor, the latter playing a pivotal role in the development of silicon-based planar process technology. This innovation, pioneered by Jean Hoerni and Robert Noyce, was crucial for the creation of the first practical integrated circuit by Noyce and independently by Jack Kilby of Texas Instruments. The subsequent MOSFET, developed by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959, became the dominant architecture for modern very-large-scale integration.

Principles of operation

A transistor operates by using a small input signal to control a much larger output signal, functioning as either an amplifier or a switch. In a bipolar junction transistor, current between the collector and emitter is controlled by the current applied to the base. In a field-effect transistor, the voltage applied to the gate terminal creates an electric field that controls the conductivity of a channel between the source and drain. This control is enabled by the properties of semiconductor materials like silicon or gallium arsenide, and the behavior of charge carriers—electrons and holes—at p–n junctions. The specific characteristics are described by various models, including the Ebers–Moll model for bipolar devices.

Types of transistors

Transistors are broadly categorized by their structure and mechanism. Bipolar junction transistors are current-controlled devices. Field-effect transistors are voltage-controlled devices and include several major families: the metal–oxide–semiconductor field-effect transistor, the junction gate field-effect transistor, and the metal–semiconductor field-effect transistor. The MOSFET is by far the most common transistor in digital and analog circuits. Other important types include the insulated-gate bipolar transistor, which combines aspects of MOSFETs and BJTs for power control, and heterojunction bipolar transistors, which use materials like gallium arsenide for high-frequency applications. Specialized forms include phototransistors and multiple-gate MOSFETs like the FinFET.

Manufacturing

Transistor fabrication is a core part of semiconductor device fabrication, involving highly complex processes performed in cleanroom facilities. The dominant material is crystalline silicon, which is grown into ingots and sliced into wafers. Processes such as photolithography, ion implantation, chemical vapor deposition, and etching are used to define the microscopic transistor structures on the wafer. Key manufacturing breakthroughs include the planar process and CMOS technology. Leading manufacturers, known as foundries, include Taiwan Semiconductor Manufacturing Company, Samsung Electronics, and Intel. The relentless miniaturization of transistors, as described by Moore's law, has driven the industry for decades.

Applications

Transistors are ubiquitous in modern technology. In digital circuits, particularly in microprocessors, memory chips, and logic gates, they function as on/off switches, forming the basis of binary computation. In analog circuits, they are used to amplify signals in devices like radio receivers, audio amplifiers, and operational amplifiers. They are essential in power supply regulation, radio frequency amplification for cellular networks, and as drivers for light-emitting diodes and motors. The proliferation of transistors enabled the development of the personal computer, the Internet, and modern consumer electronics like smartphones.

Figures of merit

Key parameters define a transistor's performance and suitability for an application. For switching and digital use, important metrics include switching speed, propagation delay, and power dissipation. For amplification, critical figures are gain, bandwidth, and noise figure. General parameters include the transition frequency, which indicates the frequency at which gain drops to unity, and maximum power dissipation. In MOSFETs, the threshold voltage and transconductance are fundamental. For power devices, breakdown voltage and on-state resistance are paramount. These characteristics are detailed in manufacturer datasheets and are central to electronic circuit design.

Category:Transistors Category:American inventions Category:Semiconductor devices