CK722 Classic Germanium Transistor Website and Museum Photo Gallery Photograph Page2

THE CK722 CLASSIC

GERMANIUM TRANSISTOR MUSEUM

A BRIEF INTRODUCTION TO EARLY TRANSISTORS

The transistor was invented by John Bardeen, Walter Brattain and William Shockley at Bell Labs in December, 1947. Announced to the public in June, 1948, this new device had characteristics which could be exploited to overcome some fundamental limitations of vacuum tubes - transistors had very long life, were small, lightweight and mechanically rugged, and required no filament current. The commercial use of transistors increased dramatically in the 1950’s, beginning with telephone switching equipment and military computers in 1952, hearing aids in 1953, and portable radios in 1954. In 1953, over 1,000,000 transistors were manufactured; in 1955, 3,500,000 transistors were manufactured, and by 1957, annual production was a staggering 29,000,000 units. The rapid rise of the transistor in the 1950’s can be attributed to a few major companies, such as Raytheon, Western Electric, RCA, Philco, General Electric, Texas Instruments, and Fairchild.

Point Contact Transistors: The first transistors utilized a technology known as point contact, which is a technique similar to that used to manufacture silicon radar mixer diodes during WWII. In a point contact transistor, two tiny sharpened wires are pressed into a small block of germanium; in this configuration, current flow between the two wires can be controlled by current flow introduced into the germanium block. Point contact transistors never achieved large volume production or commercial usage, mostly because the manufacturing process was quite unpredictable, with final device performance depending on such parameters as the physical placement of the two wires to within .001 of an inch. The earliest point contact units had small holes in the case to allow for adjustment of the wire placement and downward pressure to achieve desired performance. Another negative aspect of point contact transistor performance is excessive noise - these devices are very noisy and are not suitable for most amplifier type applications, whether in a radio or a hearing aid. Point contact transistors did find limited usage as switches, in such equipment as telephone switches and digital computers. The first commercially available point contact transistor was the Raytheon CK703, introduced in 1948. Several companies entered the transistor manufacturing business initially with point contact units, but because of the inherent limitations of this type of device, volumes were low and the technology was superceded by a new type of transistor, called a junction transistor. After 1954, there was almost no point contact transistor manufacturing, although Western Electric continued to produce the 2N110, a point contact switching unit, until the 1960’s.

Junction Transistors: Junction transistor theory was developed by William Shockley at Bell Labs in 1949, shortly after the point contact transistor had been patented and low volume manufacturing of point contact units had begun. By July, 1951, high quality junction units were also being manufactured in small numbers by Bell Labs. Junction transistors overcame many of the limitations of point contact transistors. For instance, junction units were able to operate quite well as amplifiers, because inherent noise levels were low. Equally as important, the manufacturing processes for junction transistors could be made much more predictable than the “hand-adjusted” approach needed for point contact units. With overall better performance and with more manageable manufacturing processes, the junction transistor quickly obsoleted the original point contact type. Although initial yield levels and performance parameters of junction transistors were low and with somewhat wide variability, many companies entered the race to develop the “best” manufacturing techniques for high volume junction transistor production. The M-1752 was the first commercial quality junction type transistor manufactured by Bell Labs; exploratory data sheets for this unit were available in late 1951. By July 1952, the M-1752 manufacturing process had been improved to the point that large scale production was planned by Western Electric and the standard RTMA model numbers (2N27, 2N28 and 2N29) had been assigned to versions of this first commercial junction transistor.