Why the Transistor Beat the Vacuum Tube
Early computers were built from thousands of glass valves. The ENIAC used more than 17,000 vacuum tubes, filled a room and failed regularly. The device that replaced them, demonstrated at Bell Labs in December 1947, was smaller than a fingernail and did the same basic job: switch and amplify.
The tube problem
A vacuum tube works by boiling electrons off a heated filament and controlling their flow through a vacuum. It needs a heater, so it wastes power and produces heat; its glass envelope can break; and its filament eventually burns out. Scaling up meant more heat and more failures, which is why early machines had crews swapping tubes daily.
A switch made of sand
John Bardeen and Walter Brattain, working under William Shockley, showed that a small current at one contact on a germanium crystal could control a much larger current through it. Shockley's later junction transistor was easier to manufacture, and by the mid-1950s transistors were in portable radios, hearing aids and telephone exchanges.
Integration, then scaling
The real revolution came when several transistors — then thousands, then billions — could be built on one piece of silicon. Integrated circuits removed the cost of wiring components together, and the industry discovered that smaller transistors were also faster and cheaper per unit. That feedback loop is what Gordon Moore described in 1965, and it ran for half a century.
Knowledge check
Two questions, no score
What makes a transistor better than a vacuum tube for computing?
Why did integrated circuits matter so much?
Now prove it
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