Transistor Invented

In December 1947, researchers at Bell Telephone Laboratories in New Jersey demonstrated the first working transistor, a small solid-state device that could amplify electrical signals and act as a switch. It was built by John Bardeen and Walter Brattain, working within a group led by William Shockley. The transistor replaced bulky, fragile vacuum tubes and became the basic building block of modern electronics, making possible everything from pocket radios to computers and smartphones.

The background lay in the needs of the telephone network. AT&T, Bell Labs' parent company, relied on vacuum tubes to amplify long-distance signals, but tubes were large, hot, power-hungry and prone to burning out. Bell Labs leaders wanted something more reliable. Before World War II, Shockley and others had begun exploring semiconductors, materials such as germanium and silicon whose ability to conduct electricity falls between that of metals and insulators. Wartime work on radar had improved the purity of these materials, and research resumed in earnest in 1945 under a dedicated solid-state physics group.

The breakthrough came from experiments on germanium. Bardeen, a theorist, and Brattain, an experimentalist, found that two closely spaced gold contacts pressed against a crystal could control current and produce amplification. This device is known as the point-contact transistor. Bell Labs demonstrated it to colleagues in late December 1947, and it was announced publicly the following year. Shockley, who was not an author of the key experiments, soon devised a more robust design, the junction transistor, which was easier to manufacture and became the basis for later devices. The name "transistor" is usually credited to a combination of "transfer" and "resistor."

Early transistors were used in hearing aids and then in portable radios in the mid-1950s. Silicon gradually replaced germanium because it handled heat better and was cheaper. In 1956, Bardeen, Brattain and Shockley shared the Nobel Prize in Physics for their work. Shockley later moved to California and founded a semiconductor company, and some of his staff left to start Fairchild Semiconductor, helping seed the region that would become known as Silicon Valley.

The transistor's greatest legacy came when many of them could be fabricated together. The integrated circuit, developed independently by Jack Kilby and Robert Noyce in the late 1950s, packed multiple transistors onto a single chip, and the microprocessor of the early 1970s put an entire processor on one. Since then, the number of transistors on a chip has grown from thousands to billions, driving the rapid growth of computing power and falling costs. Few inventions of the twentieth century have shaped daily life so thoroughly, though most people never see the devices at work.