Technology & Medicine › Atomic & space age › Electronic computer (Z3, Colossus, ENIAC)
Transistor
December 1947 (Bell Labs)· Invention or discovery· Communication & computing
Well documentedSolid records, physical evidence or scientific consensus.
The transistor is a tiny solid-state switch and amplifier made from semiconductor crystal; it replaced bulky vacuum tubes.
See it on the Technology & Medicine map →How it works
A transistor uses a small current or voltage to control a larger one, so it can amplify a signal or switch on and off. In December 1947 John Bardeen and Walter Brattain at Bell Labs in New Jersey built the first, a germanium 'point-contact' device; their boss William Shockley devised the sturdier junction transistor in 1948. Silicon largely replaced germanium by the 1960s. A modern chip holds billions of transistors, each smaller than most viruses.
Why it mattered
It made electronics small, cheap and reliable, leading to chips, computers, phones and the digital economy. It is the most-manufactured human-made object in history.
How we know
Bell Labs notebooks from December 1947, the 1948 public announcement and patents. Bardeen, Brattain and Shockley shared the 1956 Nobel Prize in Physics.
Still unknown or debated
Julius Lilienfeld patented a field-effect transistor idea in 1925–28, and two German engineers in Paris built a similar 'transistron' in 1948; how much priority they deserve is debated.
Inside this (1)
Connections (7)
▸Telephone paid for the Bell Labs research behind the TransistorMostly agreed
The connection
AT&T's Bell System, the US telephone monopoly, funded Bell Labs, among the world's richest research centers. It wanted something better than the vacuum tubes that amplified long-distance calls and the mechanical relays that switched them, since tubes ran hot and burned out. That goal led directly to the 1947 transistor.
When and how
Bell Labs, Murray Hill, New Jersey; research director Mervin Kelly set up a solid-state physics group under William Shockley in 1945.
How sure are we?
Bell Labs memos and Kelly's stated aims are well documented; AT&T licensed the transistor patent widely from 1952, partly under antitrust pressure.
Debates and open questions
Economists debate whether monopoly profits are needed to fund such basic research, or whether Bell Labs was a one-off of its era.
▸Vacuum tube was replaced by the TransistorWell documented
The connection
The transistor did a vacuum tube's jobs, amplifying and switching, with a speck of crystal instead of a heated filament in a glass bulb. It was smaller, used far less power, gave off little heat and lasted for years. Through the 1950s and 1960s transistors replaced tubes in radios, computers and telephone systems.
When and how
Bell Labs, New Jersey, 1947; transistor radios from 1954; transistor computers from 1953–55; most consumer tubes gone by the 1970s.
How we know
Industry production records and product histories trace the switch; Bell Labs said from the start that replacing tubes was the goal.
Debates and open questions
Tubes never fully vanished: high-power transmitters, microwave ovens' magnetrons and many guitar amplifiers still use them, and audiophiles argue over their warmer sound.
▸Radio went pocket-sized with the TransistorWell documented
The connection
Tube radios were furniture-sized and needed wall power. Transistors used so little power that a radio could run on a small battery and fit in a pocket. The Regency TR-1 (1954) came first; Sony's models followed from 1955, and cheap transistor radios spread news and music worldwide.
When and how
Regency TR-1, Indianapolis, October 1954, with Texas Instruments transistors; Sony, then called Tokyo Tsushin Kogyo, Tokyo, from 1955.
How we know
Surviving radios, sales figures and company histories; the TR-1 sold roughly 150,000 units.
Debates and open questions
The influence ran both ways: radio sets had long used crystal detectors, the semiconductor ancestor of the transistor, so radio helped create the transistor too.
▸Radar spurred the semiconductor research behind the TransistorMostly agreed
The connection
Wartime microwave radar needed crystal detectors that could handle signals too fast for tubes. US and British labs learned to purify germanium and silicon to make them, building expertise in semiconductors, materials whose conductivity can be tuned. Bell Labs' transistor team built directly on that wartime crystal work.
When and how
MIT Radiation Laboratory, Purdue University, the University of Pennsylvania and Bell Labs, 1940–45; Russell Ohl found the silicon p–n junction at Bell Labs in 1940.
How sure are we?
Wartime research reports and Bell Labs histories show the transistor team used materials and methods from radar crystal work.
Debates and open questions
Purdue researchers saw related effects by 1947; why Bell Labs got to the transistor first is a classic case study in research management.
▸Electronic computer (Z3, Colossus, ENIAC) was shrunk by the TransistorWell documented
The connection
Tube computers filled rooms, drew as much power as a small factory and broke down often. Transistors did the same switching while being smaller, cooler and more reliable. Manchester's transistor computer ran in 1953, and from 1959 IBM's transistorized 7090 and 1401 became standard machines for science and business.
When and how
University of Manchester, 1953; Bell Labs' TRADIC for the US Air Force, 1954; IBM 7090 and 1401, 1959.
How we know
Machine records show size, power use and failure rates falling sharply with transistors; IBM's 1401 sold more than 10,000 units.
Debates and open questions
Some early transistors were less reliable than tubes; how quickly the switch paid off depended on manufacturing quality, which improved fast but unevenly.
▸Transistor was miniaturised into the Integrated circuit (microchip)Well documented
The connection
By the late 1950s, electronics needed thousands of transistors, each wired in by hand, and every solder joint could fail: engineers called it the 'tyranny of numbers.' Kilby and Noyce realised transistors, resistors and capacitors could all be made from the same semiconductor, so a whole circuit could be formed in one piece.
When and how
Kilby at Texas Instruments in Dallas, summer 1958; Noyce at Fairchild Semiconductor in what became Silicon Valley, 1959, using Jean Hoerni's flat 'planar' transistor process.
How we know
Kilby's dated lab notebook and Noyce's 1959 patent application describe transistors and other parts built together on one piece of semiconductor.
Debates and open questions
Whether the chip was a leap or an obvious next step is debated: British engineer Geoffrey Dummer proposed the idea in 1952, and several labs were close by 1958.
▸Transistor led, via silicon solar cells, to Cheap solar, batteries and electric carsMostly agreed
The connection
Transistor work made Bell Labs expert at purifying and doping silicon, adding traces of other elements to control its electrical behavior. In 1954 Daryl Chapin, Calvin Fuller and Gerald Pearson used that know-how to make the first practical silicon solar cell, about 6% efficient. Transistor-based power electronics also run solar inverters, wind turbines and electric car motors.
When and how
Bell Labs, Murray Hill, New Jersey: transistor 1947, solar cell announced April 1954; cells powered the Vanguard 1 satellite in 1958.
How sure are we?
Bell Labs records and the 1954 announcement tie the solar cell to transistor-era silicon research; Fuller had developed doping methods for transistors.
Debates and open questions
Solar cells also built on earlier discoveries, the photovoltaic effect (Becquerel, 1839) and selenium cells (1883), so the transistor is one root among several.