View source for CK722

{{short description|First low-cost transistor available to the general public, introduced in 1953}}
[[File:CK722.JPG|thumb|CK722 transistor and package]]
The '''CK722''' was the first low-cost junction [[transistor]] available to the general public. It was a [[Bipolar junction transistor#PNP|PNP]] [[germanium]] small-signal unit. Developed by [[Norman Krim]], it was introduced by [[Raytheon]] in early 1953 for $7.60 each; the price was reduced to $3.50 in late 1954 and to $0.99 in 1956. Norm Krim selected [[Radio Shack]] to sell the CK721 and CK722 through their catalog. Krim had a long-standing personal and business relationship with Radio Shack.<ref>{{cite web |last=Ward |first=Jack |title=Norm Krim{{snd}} The Father of the CK722 |url=http://semiconductormuseum.com/Museum_Index.htm}}</ref> The CK722s were selected "fall out" from the Raytheon's premium-priced CK721 (which are fallouts from CK718 hearing-aid transistors).<ref name ="PE Oct 1979">{{Cite magazine | last = Garner | first = Lou | title = Solid State: Down Nostalgia Lane |magazine= Popular Electronics | volume = 16 | issue = 4 |pages=86, 87, 92 | publisher = Ziff-Davis | location = New York | date = October 1979 | url = http://www.swtpc.com/mholley/PopularElectronics/Oct1979/PE_Oct1979.htm}}</ref> Raytheon actively encouraged hobbyists with design contests and advertisements.<ref name = "PM Jun 1953">{{Cite magazine | title = $10,000 in Prizes. Enter Raytheon's Transistor Application Contest! |magazine= Popular Mechanics | volume = 99 | issue = 6 | page =219 | publisher = Popular Mechanics Co. | location = Chicago | date = June 1953 | url = https://books.google.com/books?id=mdwDAAAAMBAJ&pg=PA219 | issn = 0032-4558}} Raytheon sponsored a design contest for applications that used the CK722 transistor. The top prize was $5,000.</ref><ref name = "PE Apr 1954">{{Cite magazine | title = 8 Transistor circuits you build with Raytheon CK722 transistors |magazine= Popular Electronics | volume = 2 | issue = 4 | page =8 | publisher = Ziff-Davis | location = New York | date = April 1955}} [[:File:Raytheon CK722 April 1955.jpg|CK722 advertisement]].</ref>

In the 1950s and 1960s, hundreds of hobbyist electronics projects based around the CK722 transistor were published in popular books and magazines.<ref name = "PM Oct 1953">{{Cite magazine | title = How to Build Experimental Transistor Receivers |magazine= Popular Mechanics | volume = 100 | issue = 4 | pages =246–248 | publisher = Popular Mechanics Co. | location = Chicago | date = October 1953  | url = https://books.google.com/books?id=P9wDAAAAMBAJ&pg=PA246}}</ref><ref name = "PM Nov 1957">{{Cite magazine |last = Garner | first = Lou | title = Transistorized Instrument Amplifier |magazine= Popular Mechanics | volume = 108 | issue = 5 | pages =160–162 | publisher = Popular Mechanics Co. | location = Chicago | date = November 1957 | url = https://books.google.com/books?id=oeEDAAAAMBAJ&pg=PA160}}</ref> Raytheon also participated in expanding the role of the CK721/CK722 as a hobbyist electronics device by publishing "Transistor Applications" and "Transistor Applications{{snd}} Volume 2" during the mid-1950s.

[[File:1950's Raytheon Transistor Applications for Experimenters and Hobbyist.JPG|thumbnail|Transistor application books for CK722 by Raytheon]]
[[File:Mid 1950 Raytheon Transistors- Size Comparison.jpg|thumbnail|Size comparison and metal case colors of Raytheon hearing aid transistors on the left and the CK721 (blue) and CK722 (silver) on the right. The rejected hearing aid transistors would be inside the metal cases of the CK721 and CK722.]]

== Construction ==
The original CK722 were direct fallouts from CK718 hearing-aid transistors that did not meet specifications. These fallouts were later stamped with CK721 or CK722 numbers based on gain, noise and other dynamic characteristics. Early CK722s were plastic-encapsulated and had a black body. As Raytheon improved its production of hearing-aid transistors with the introduction of the smaller CK78x series, the body of the CK721/CK722s was changed to a metal case. Raytheon, however, kept the basic body size and used a unique method by taking the smaller CK78x rejects and inserting it into the larger body and sealing it. The first metal-cased CK721/CK722s were blue, and the later ones were silver. More details of this can be found in Jack Ward's website, Semiconductor Museum or the CK722 Museum, see external link reference below.

==Engineers associated with the CK722 ==

=== Norman Krim – father of the transistor hobbyist market ===
In the late 1930s, [[Norman Krim|Norm Krim]], then an engineer for Raytheon, was looking into subminiature tubes for use in consumer applications such as hearing aids and pocket radios. Krim's team developed the CK501X subminiature amplifier tube that could run on penlight A type batteries or small 22.5&nbsp;V B-type batteries.

Following World War II, Krim was interested in developing the first pocket vacuum tube radio. Raytheon approved, and a team headed by Krim designed a set of subminiature tubes specifically for radios (2E32, 2E36, 2E42 and 2G22). Raytheon’s acquisition of Belmont Radio proved prescient, and the result was the Belmont Boulevard in 1945. The radio did not sell well, and Raytheon took a loss. Despite this setback, Krim remained at the company and shifted his attention to the newly developed transistor.<ref>{{cite book |last=Schiffer |first=Michael Brian |title=The Portable Radio in American Life |year=1991 |publisher=The University of Arizona Press |location=Tucson, AZ |isbn=0816512841 |pages=161–165}}</ref>

===Carl David Todd – participant in the CK722 design contest ===
Carl Todd, a hobbyist and later engineer in GE’s transistor division, placed 6th in Raytheon's CK722 design contest. His hobby work with this early transistor inspired him to pursue electrical engineering as a career. As an engineer, he helped develop the [[2N107]] transistor, GE's alternative to the CK722.<ref>[http://www.semiconductormuseum.com/Transistors/GE/OralHistories/Todd/Todd_Index.htm Jack Ward's interview with Carl Todd].</ref>

==See also==
* [[Alfred Powell Morgan]] – an author of youth-oriented books on early electronics

==References==
{{reflist|30em}}

==External links==
{{Commons category|CK722}}
*A general summary of Norman Krim's achievements can be seen at this IEEE link [https://spectrum.ieee.org/in-memoriam-norman-krim In Memoriam- Norm Krim ]
*Jack Ward's Semiconductor Museum-[http://www.ck722museum.com/ The CK722 transistor website and museum]
*Harry Goldstein's IEEE article on celebrating the transistor- {{Cite journal | last = Goldstein | first = Harry | title = The Irresistible Transistor | journal =  IEEE Spectrum| volume = 40 | issue = 3 | pages =42–47 | publisher = IEEE | date = March 2003 | doi = 10.1109/MSPEC.2003.1184435 }} webarchive backup: [https://web.archive.org/web/20091112194900/https://spectrum.ieee.org/biomedical/devices/the-irresistible-transistor/0 Free version]

[[Category:Commercial transistors]]
[[Category:History of electronic engineering]]
[[Category:Bipolar transistors]]