The transistor is a three terminal, solid state electronic device. In a three terminal device we can control electric current or voltage between two of the terminals by applying an electric current or voltage to the third terminal.

This three terminal character of the transistor is what allows us to make an amplifier for electrical signals, like the one in our radio. With the three-terminal transistor we can also make an electric switch, which can be controlled by another electrical switch. By cascading these switches (switches that control switches that control switches, etc.) we can build up very complicated logic circuits.

The transistor was not the first three terminal device. The vacuum tube triode preceded the transistor by nearly 50 years. Vacuum tubes played an important role in the emergence of home electronics and in the scientific discoveries and technical innovations which are the foundation for our modern electronic technology.

Thomas Edison’s light bulb was one of the first uses of vacuum tubes for electrical applications. Soon after the discovery of the light bulb, a third electrode was placed in the vacuum tube to investigate the effect that this electrode would have on “cathode rays,” which were observed around the filament of the light bulb.

Joseph John Thomson developed a vacuum tube to carefully investigate the nature of cathode rays, which resulted in his discovery, published in 1897. He showed that the cathode rays were really made up of particles, or “corpuscles” as Thomson called them, that were contained in all material. Thomson had discovered the electron, for which he received the Nobel Prize in Physics 1906.

The First Transistor
In 1947, John Bardeen and Walter Brattain, working at Bell Telephone Laboratories, were trying to understand the nature of the electrons at the interface between a metal and a semiconductor. They realized that by making two point contacts very close to one another, they could make a three terminal device - the first “point contact” transistor.

They quickly made a few of these transistors and connected them with some other components to make an audio amplifier. This audio amplifier was shown to chief executives at Bell Telephone Company, who were very impressed that it didn’t need time to “warm up” (like the heaters in vacuum tube circuits). They immediately realized the power of this new technology.

Bell Labs kept their discovery quiet until June 1948. They then announced it in a fanfare of publicity, but few people realised its significance, and it did not even make the front page of the newspapers. Shockley basically ignored the point-contact transistor, and continued his research in other directions. He modified his original ideas and developed the theory of the junction transistor. In July 1951, Bell announced the creation of such a device. In September 1951 Bell held a transistor symposium, and licensed their technology for both types of transistor to anyone who paid the required fee of 25 thousand dollars. This was the start of the transistor industry which has changed the way that we live, in the Western world at least.

This invention was the spark that ignited a huge research effort in solid state electronics. Bardeen and Brattain received the Nobel Prize in Physics, 1956, together with William Shockley, “for their researches on semiconductors and their discovery of the transistor effect.” Shockley had developed a so-called junction transistor, which was built on thin slices of different types of semiconductor material pressed together. The junction transistor was easier to understand theoretically, and could be manufactured more reliably.

The transistor is an influential invention that changed the course of history for computers. The first generation of computers used vacuum tubes; the second generation of computers used transistors; the third generation of computers used integrated circuits; and the fourth generation of computers used microprocessors.

Tag: The Transistor