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At Bell Telephone Laboratories on December 16, 1947, physicists John Bardeen and Walter Brattain attached three flimsy metal contacts to a thin sliver of the element germanium, applied an electric signal, and discovered that the signal emerging from their device was nearly a hundred times stronger than the one that went in. Unveiled a week later to Bell Labs executives, the new solid-state amplifier-soon dubbed a “transistor”-was “a magnificent Christmas present,” in the words of research group leader William Shockley, who only a month later conceived an improved version that eventually proved far easier to manufacture.

Fifty years later, transistors have shrunk so dramatically that they are now invisible to the unaided eye. Yet as the crucial ingredients in every microchip, acting as microscopic pumps and valves that regulate the flow of electric current, these minuscule devices continue to have a tremendous impact on almost every aspect of modern life.

It was obvious at the time that Bardeen and Brattain’s unwieldy contraption represented a breakthrough in electronics. But its inventors thought of it mainly as a replacement for vacuum tubes, which were used as amplifiers and switches in telephone equipment, radios, and most other electronic devices. Shockley had perhaps the best intuition of what was to come. “There has recently been a great deal of thought spent on electronic brains or computing machines,” he speculated in December 1949. “It seems to me that in these robot brains the transistor is the ideal nerve cell.”

The physical process Bardeen, Brattain, and Shockley discovered now lies at the throbbing heart of an electronics industry that generates worldwide sales of more than $1 trillion annually. The transistor’s greatest value is that it can be so drastically miniaturized: its fundamental operating principles have remained essentially unaltered as its linear dimensions have shrunk more than 10,000-fold. By contrast, vacuum tubes had absolutely no prospects for the kind of astonishing miniaturization that has occurred in solid-state devices. And the tubes’ other problems-they were balky, burned out too frequently, generated too much heat, and consumed too much power-proved completely insurmountable.

The first transistors were typically a centimeter long; by the late 1950s, they were measured in millimeters. With the invention of the integrated circuit in 1958, the stage was set for a steady parade of further innovations that reduced the size of transistors to submicron levels-less than a millionth of a meter. Today the transistor is little more than an abstract physical principle imprinted innumerable times on narrow slivers of silicon-millions of microscopic ripples on a shimmering crystal sea. As Intel’s cofounder Gordon Moore recently noted, there are more transistors made every year than raindrops falling on California, and producing one costs less than printing a single character in a newspaper.

“The synergy between a new component and a new application generated an explosive growth of both,” observed Moore’s longtime partner Robert Noyce, reflecting on how the transistor and computer grew up together. He made this comment in 1977, a few years before the personal computer began to stimulate yet another commercial explosion based on semiconductors. More than any other factor, the fantastic shrinkage of the transistor in both size and cost is what has allowed the average person to own and operate a computer that is far more powerful than anything the armed services or major corporations could afford a few decades ago. If we had instead had to rely on vacuum tubes, for example, the computing power of a Pentium chip would require a machine as big as the Pentagon.

And just this past year-which also happens to be the centennial of the electron’s discovery-there have been successful attempts to build transistors so small that they involve the transmission of only one electron through a channel less than 10 nanometers long. If this technology can ever be transferred to the production line, another hundredfold reduction in the size of transistors may be in the offing.

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