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A transistor lets an electrical input control current. That control makes it possible to amplify a signal or switch a circuit on and off. The first successful transistor, built in 1947, used two gold contacts on germanium; later junction and MOS designs made transistor technology more practical to manufacture and apply.
How does a transistor work?
A transistor uses a semiconductor to let one electrical signal control current elsewhere in a circuit. In an amplifier, a small input variation can produce a larger variation in the controlled current. As a switch, the transistor’s input determines whether current flows through a circuit path.
Think of the input as a control that governs a larger flow. The analogy is useful, but the device is not a mechanical valve: charge carriers and internal electrical fields in the semiconductor produce the control.
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How the first transistor demonstrated the idea
On December 16, 1947, John Bardeen and Walter Brattain achieved transistor action with a point-contact device. Two closely spaced gold contacts rested on high-purity germanium. Applying voltage at one contact modulated current through the other, allowing the device to amplify a signal. Bell Labs demonstrated it to officials on December 23, then announced it publicly on June 30, 1948. Computer History Museum timeline
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The early device could amplify an input signal up to 100 times, according to the Computer History Museum’s historical account. That figure describes this point-contact design, not transistors in general. Its construction was mechanically delicate, an important reason the first successful demonstration was not the end of transistor development. Computer History Museum account of the transistor
How transistor designs developed
| Type | Structure and control | Manufacturing practicality | Historical role |
|---|---|---|---|
| Point-contact transistor | Two closely spaced gold contacts on germanium; voltage at one contact modulated current through the other. | Mechanically delicate. | The 1947 proof that a semiconductor device could provide transistor action and amplification. |
| Junction transistor | A three-layer p-type/n-type semiconductor structure; bipolar operation involves minority-carrier injection. | Production depended on improvements in material purity and manufacturing. Grown-junction designs advanced practicality. | A distinct structure conceived by William Shockley in January 1948 and developed toward production in the following years. |
| MOS transistor | An insulated-gate field-effect structure, distinct from the point-contact and junction designs. | The successful demonstration followed work to address surface states that had blocked field-effect operation. | Mohamed Atalla and Dawon Kahng demonstrated the first successful insulated-gate MOS transistor at Bell Labs in 1960. |
Junction transistors made production more practical
Shockley conceived the junction transistor in January 1948. In 1951, Gordon Teal and Morgan Sparks developed grown-junction devices using single-crystal germanium and successive dopants; these surpassed the best point-contact transistors in performance. Their development illustrates the shift from a delicate laboratory device toward structures that could be manufactured more consistently. Computer History Museum: grown-junction transistors
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Silicon broadened the material options
Bell Labs chemist Morris Tanenbaum fabricated a silicon transistor in January 1954. Texas Instruments later made silicon transistors and announced that they were in production and available for sale. Silicon’s operating characteristics helped it compete with germanium in practical applications. Computer History Museum: first silicon transistor
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In 1960, Mohamed Atalla and Dawon Kahng demonstrated the first successful insulated-gate MOS field-effect transistor at Bell Labs. This was not simply another version of the point-contact device: it used a different architecture, and its success depended on overcoming surface-state problems that had hindered field-effect operation. Computer History Museum: MOS transistor demonstrated
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Why the transistor changed electronics
The transistor combined two useful functions—amplifying signals and switching current—in a semiconductor device. The move from delicate contacts to junction structures, improved materials, and then MOS designs expanded the range of ways transistors could be made and used. That progression, rather than the first device alone, explains why the transistor became a foundation of modern electronics.
The work was not the achievement of one person or one laboratory. Bardeen and Brattain made the 1947 point-contact device; Shockley conceived the junction approach; Teal and Sparks advanced grown-junction production; and Atalla and Kahng demonstrated the MOS transistor. In Europe, Herbert Mataré and Heinrich Welker obtained reproducible amplification in 1948, and thousands of their devices had been manufactured for the French telephone system by mid-1949. Computer History Museum: European transistor
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Bell Labs’ public announcement, dated July 1, 1948, captured the uncertainty and promise of the early moment: “Although the device is still in the laboratory stage, Bell scientists and engineers expect it may have far-reaching significance in electronics and electrical communication.” The Computer History Museum reproduces the announcement in its archive. Computer History Museum archive of the Bell Labs announcement
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