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The CK722 was the first low cost junction transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...

 available to the general public. It was a PNP germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 small signal unit. It was introduced by Raytheon
Raytheon Company is a major American defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics. It was previously involved in corporate and special-mission aircraft until early 2007...

in early 1953 for $7.60 each; the price was reduced to $3.50 in late 1954 and to $0.99 in 1956 The CK722s were selected "fall out" from the Raytheon's premium-priced hearing-aid transistors. Raytheon actively encouraged hobbyist with design contest and advertisements.

In the 1950s and 1960s, hundreds of hobbyist electronics projects based around the CK722 transistor were published in popular books and magazines.

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