CK722

CK722 transistor and package

The CK722 was the first low-cost junction transistor available to the general public. It was a 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.[1] The CK722s were selected "fall out" from the Raytheon's premium-priced CK721 (which are fallouts from CK718 hearing-aid transistors).[2] Raytheon actively encouraged hobbyists with design contests and advertisements.[3][4]

In the 1950s and 1960s, hundreds of hobbyist electronics projects based around the CK722 transistor were published in popular books and magazines.[5][6] Raytheon also participated in expanding the role of the CK721/CK722 as a hobbyist electronics device by publishing "Transistor Applications" and "Transistor Applications – Volume 2" during the mid-1950s.

Transistor application books for CK722 by Raytheon
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.
  1. ^ Ward, Jack. "Norm Krim – The Father of the CK722".
  2. ^ Garner, Lou (October 1979). "Solid State: Down Nostalgia Lane". Popular Electronics. Vol. 16, no. 4. New York: Ziff-Davis. pp. 86, 87, 92.
  3. ^ "$10,000 in Prizes. Enter Raytheon's Transistor Application Contest!". Popular Mechanics. Vol. 99, no. 6. Chicago: Popular Mechanics Co. June 1953. p. 219. ISSN 0032-4558. Raytheon sponsored a design contest for applications that used the CK722 transistor. The top prize was $5,000.
  4. ^ "8 Transistor circuits you build with Raytheon CK722 transistors". Popular Electronics. Vol. 2, no. 4. New York: Ziff-Davis. April 1955. p. 8. CK722 advertisement.
  5. ^ "How to Build Experimental Transistor Receivers". Popular Mechanics. Vol. 100, no. 4. Chicago: Popular Mechanics Co. October 1953. pp. 246–248.
  6. ^ Garner, Lou (November 1957). "Transistorized Instrument Amplifier". Popular Mechanics. Vol. 108, no. 5. Chicago: Popular Mechanics Co. pp. 160–162.