Inventing the Transistor

Scientists in the 1920s proposed building amplifiers from semiconductors. But they didn’t understand the materials well enough to actually do it. In 1939, William Shockley at AT&T’s Bell Labs revived the idea as a way to replace vacuum tubes.

Under Shockley’s direction, John Bardeen and Walter Brattain demonstrated in 1947 the first semiconductor amplifier: the point-contact transistor, with two metal points in contact with a sliver of germanium. In 1948, Shockley invented the more robust junction transistor, built in 1951.

The three shared the 1956 Nobel Prize in Physics for their inventions.

How Bardeen and Brattain's Transistor Worked

Bardeen and Brattain’s transistor consisted of a sliver of germanium with two closely spaced gold point contacts held in place by a plastic wedge. They selected germanium material that had been treated to contain an excess of electrons, called N-type. When they caused an electric current to flow through one contact (called the emitter) it induced a scarcity of electrons in a thin layer (changing it locally to P-type) near the germanium surface. This changed the amount of current that could flow through the collector contact. A small change in the current through the emitter caused a larger change in the collector current. They had created a current amplifier.

Transistors Take Off

AT&T, which had invented the transistor, licensed the technology in 1952. It hoped to benefit from others’ improvements.

Transistors swiftly left the lab and entered the marketplace. Although costlier than vacuum tubes, they were ideal when portability and battery operation were important. The 1952 Sonotone hearing aid was America’s first transistorized consumer product. AT&T also used transistor amplifiers in its long distance telephone system. They soon appeared as switches, beginning with an experimental computer at Manchester University in 1953.

As prices dropped, uses multiplied. By 1960, most new computers were transistorized.