Vacuum tube op amps continued to flourish for some time into the 1950’s and 1960's, but their competition was eventually to arrive from solid-state developments. These took the form of several key innovations, all of which required a presence before effective solid-state op amp designs could be established. This discussion treats modular and hybrid solid-state op amps, which preceded and overlapped solid-state IC op amps.
There were three of these key developments, the invention of the transistor, the invention of the integrated circuit (IC), and the invention of the planar IC process. A detailed history of solid-state inventions and related process developments can be found in articles celebrating the transistor’s 50th anniversary, within the Autumn 1997 Bell Labs Technical Journal (References 1 and 2: Ian M. Ross, "The Foundation of the Silicon Age," Bell Labs Technical Journal, Vol. 2, No. 4, Autumn 1997 and C. Mark Melliar-Smith et al, "Key Steps to the Integrated Circuit," Bell Labs Technical Journal, Vol. 2, No. 4, Autumn 1997).
Birth of the Transistor
John Bardeen, Walter Brattain, and William Shockley of Bell Labs, working with germanium semiconductor materials, first discovered the transistor effect in December of 1947. Of course, this first step was a demonstration of gain via a new principle, using a semi-conducting material, as opposed to a vacuum tube. But more remained to be done before commercial transistors were to appear. For their achievement, the trio received the 1956 Nobel Prize in physics. In addition to vacuum tubes, circuit designers now had a lower voltage, lower power, miniature amplifying device (References 3 and 4: J. Bardeen, W. H. Brattain, "The Transistor, a Semi-Conductor Triode," Physical Review, Vol. 74, No. 2, July 15, 1947 pp. 230-231 (the invention of the germanium transistor) and W. Shockley, "The Theory of p-n Junctions in Semiconductors and p-n Junction Transistors," Bell System Technical Journal, Vol. 28, No. 4, July 1949, pp. 435-489 (theory behind the germanium transistor)).
Over the course of the next 10 years or more, various means were explored to improve the germanium transistors. The best germanium transistors were still relatively limited in terms of leakage currents, general stability, maximum junction temperature, and frequency response. Some of these problems were never to be solved. While many performance improvements were made, it was early recognized that silicon as a semiconductor material had greater potential, so this occupied many researchers.
In May of 1954, Gordon Teal of Texas Instruments developed a grown-junction silicon transistor. These transistors could operate to 150°C, far higher than germanium. They also had lower leakage, and were generally superior amplifying devices. Additional processing refinements were to improve upon the early silicon transistors, and eventually lead a path to the invention of the first integrated circuits in the late fifties.
Birth of the IC
In 1958, Jack Kilby of Texas Instruments invented the integrated circuit, now known universally as the IC (Reference 5: J. S. Kilby, "Invention of the Integrated Circuit," IRE Transactions on Electron Devices, Vol. ED-23, No. 7, July 1976, pp. 648-654 (Kilby’s IC invention at TI)). For this effort he was ultimately to become a co-recipient of the 2000 Nobel Prize in physics.
Kilby’s work, however important as it was, could arguably be said to be non-exclusive in terms of first authorship of the integrated circuit. In early 1959, Robert Noyce, an engineer at Fairchild Semiconductor, also developed an IC concept (Reference 6: Robert N. Noyce, "Semiconductor Device-and-Lead Structure," US Patent 2,981,877, filed July 30, 1959, issued April 25, 1961 (Noyce’s IC invention at Fairchild)).
The nucleus of Noyce’s concept was actually closer to the concept of today’s ICs, as it used inter-connecting metal trace layers between transistors and resistors. Kilby’s IC, by contrast, used bond wires.
As might be expected from such differences between two key inventions, so closely timed in their origination, there was no instant consensus on the true "IC inventor". Subsequent patent fights between the two inventor’s companies persisted into the 1960s. Today, both men are recognized as IC inventors.
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