The Transistor

The transistor was invented at Bell Laboratories in December 1947, not in 1948 as is often stated, by Bardeen and Brattain. The transistor could amplify an electric current like a valve but its power consuption was very low. The first transistor was made of germanium, a semiconducting material.

'Discovered' would be a better word, for although they were seeking a solid-state equivalent to the vacuum tube, it was found accidentally during the investigation of the surface states around a diode point-contact. The first transistors were therefore of the point-contact type. There is some evidence that Shockley, the theorist who was leading the research, was annoyed because he realized that this device was not what he was seeking. At the time he was trying to find a semiconductor amplifier similar to what we now call a junction FET.

Bell Labs kept their discovery quiet until June 1948, hence the confusion about the date of discovery. They then announced it in a fanfare of publicity, but few people realized the significance of the announcement, 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 they held a transistor symposium, and licensed their technology for both types of transistor to anyone who paid the required fee of 25 thousand dollars.

The next breakthrough was that scientists discovered that it was possible to improve the characteristics of the transistor by adding certain types of impurities (a process called doping) into the semiconductors. The transistor replaced the valves. The first silicon transistor was made in 1954. Silicon was cheaper than germanium and available in big quantities. The silicon transistor soon became used in electronics.

Below are two pictures of the first transistor prototypes.

Specially built amplifier, used in the invention of the transistor, was given to National Museum of American History by transistor co-inventor Walter Brattain.

This transistor was possibly the first ever commercially available. A Raytheon advertisement dated 1952 claims that the CK703 was in production in 1948. Since Bell Lab's announcement of the transistor was made in July 1948, Raytheon must have been very quick off the mark. Most publications give the CK703 a date of 1949. The CK703 was soon replaced by the improved CK716, which was visually identical apart from the type number. The top end of the cylindrical brass case has a concentric hole through it, showing the top of a short brass rod on which presumably the germanium die is mounted. Both the CK703 and CK716 suffered from difficulties of production, and they were not a commercial success. However, Raytheon went on to make the first ever mass-produced junction transistor, the CK722.

This transistor, shown in the middle in the image immediately below, was the first mass-produced transistor, manufacture started in 1953. It was a germanium PNP low-power AF type at an affordable price, and it opened up the world of semiconductors to the amateur as well as the professional. The oldest examples are black plastic cuboids, with a clearly-visible small glass block in which the lead wires were anchored. At the top in the image is a low-noise version, the CK721. At the bottom is a 'mechanical sample' which was sent to circuit designers so that they could see (and try) the size and shape of the revolutionary new component. The second image below that shows a later CK722 with a thin aluminium body, filled with plastic. Other ones had an iridescent blue metal body, unique to Raytheon and very characteristic. Many of these transistors were made, and they are still not difficult to find today.

For a "QuickTime" movie (956K) of the testing of the original transistor in 1947, click here. The file is large, so be patient while it loads. You must have QuickTime plug-in (click here to get it) for your browser to run the movie. It is worth it, though. The movie shows the oscilliscope screen displaying a small amplitude sine wave, prior to voltage being applied to the junction of the first transistor. Then the oscilliscope shows a much larger wave when the amplification is enabled by flipping the switch. WOW! A glimpse of history in the making.

Credits and thanks to Andrew Wylie of Purley, England, known as Mr. Transistor. He has provided the historical text and most pictures.