Jack Kilby with his engineering notebook in a 1997 picture. (Reuters)

San Francisco, June 22 (Reuters): Jack Kilby, inventor of the integrated circuit, the basis of the computer chip revolution and foundation of what is now a trillion-dollar industry, died of cancer on Monday.

Kilby, 81, made the discovery 47 years ago, when, as a recently hired engineer at Texas Instruments Inc., he was left to work alone in a laboratory while most of his 7,500 colleagues were taking a company-wide summer vacation leave. As a new hire, Kilby did not qualify to take a vacation in August 1958.

“It was a very quiet time and he got a lot done,” said Pat Weber, 65, a long-time colleague and friend of Kilby’s, who retired as vice chairman of Dallas-based Texas Instruments in 1998.

Kilby, a seminal 20th-century inventor whom many place in the same league as Henry Ford and the Wright Brothers, won the Nobel Prize for Physics in 2000 for his work.

By hand-wiring together multiple transistors, Kilby’s invention ? about half the size of a paper clip ? spawned a revolution in miniaturisation in which millions of circuits are now housed on tiny pieces of silicon used in devices from computers to elevators to pacemakers.

Working in parallel at pioneering Silicon Valley company Fairchild Semiconductor, Kilby’s rival Bob Noyce sketched out his own ideas for an integrated circuit in an engineering notebook ? then forgot about it, according to a new biography of Noyce’s life.

Kilby, on the other hand, immediately recognised the value of his invention and built a working prototype in a matter of days, according to associates at Texas Instruments. Development of the integrated circuit was driven by the Cold War space race with the Soviet Union after the 1957 launch of Sputnik.

“The drive was to integrate all these electronic components into one device,” said Kevin McGarity, 60, a retired former head of sales at Texas Instruments. “It sounds so simple today. But it’s actually revolutionary.”.

While the competition sparked a 25-year patent battle between the companies over royalties from the invention, the “Kilby patent” weathered all legal challenges.

Jack St. Clair Kilby was born in Jefferson City, Missouri, on November 8, 1923, and spent his childhood in rural Western Kansas. He graduated from the University of Illinois with a degree in electrical engineering in 1947 ? the year the electronic transistor was invented at AT&T.