Raytheon Ck722
The Raytheon CK722 was a low-cost PNP germanium junction transistor introduced in 1953 that became the first transistor sold in quantity to hobbyists and experimenters, and in that role it put the new device into the hands of a generation of amateur electronics builders. Its place in history is cultural rather than technical: it was neither the fastest nor the best transistor of its day, but it was cheap enough and widely enough advertised that ordinary people could buy one, wire it up on a bench and see amplification for themselves.
The CK722 was priced and packaged for the amateur, and that was its innovation. At launch it sold for about 7.60 dollars, a significant sum for a single component in 1953, but within reach of a dedicated hobbyist at a time when the alternative was a vacuum tube plus a high-voltage power supply; the price later fell considerably as production grew and competition arrived. Raytheon sold it through radio parts distributors and mail-order channels, and a small, rugged package with wire leads, usable at low voltage from a single battery, was ideal for experimenters. Earlier junction transistors were mostly sold in quantity to manufacturers; the CK722 treated the individual buyer as a market.
Magazine projects turned the device into a movement. Popular Electronics, which began publication in the autumn of 1954, along with other hobby magazines such as Radio-Electronics and manufacturers' booklets, ran construction articles for transistor radios, amplifiers, oscillators and code-practice sets built around the CK722 and its siblings. A typical project used a few resistors, capacitors, a battery, a headphone or small speaker and one or two transistors, and ran for a long time on flashlight cells, which is a very different proposition from a tube radio. Builders who learned from these projects included people who later entered the electronics industry, which is why the CK722 is sometimes credited with helping to grow a generation of engineers and technicians.
As a device, the CK722 was an ordinary low-power germanium audio transistor, with the typical limitations of the type. Being germanium, it leaked noticeably with heat, with a collector leakage current that rose steeply with temperature, and its current gain was modest and varied from unit to unit. Its frequency response was limited, which suited audio circuits better than radio-frequency ones, and it was easily damaged by a hot soldering iron or by exceeding its small voltage and power ratings. Hobby circuits that were fine on a cool bench could become unstable when warm, a first-hand lesson in biasing and thermal runaway that formal courses of the time seldom gave beginners.
A common misconception is that the CK722 was the first commercial transistor, or that it was a silicon device. Earlier point-contact and junction transistors were sold commercially to equipment makers, and silicon transistors, which tolerate heat far better, arrived from Texas Instruments in 1954 and became standard in the following years. The CK722's role was to be the first in wide hobbyist distribution. Its collector market continues today: original packages are sought after by collectors, and the model has a small cult following, the surviving examples being a physical reminder of the moment the transistor became a home-workshop component.
Its modern relevance is the lineage of accessible components that runs to today's maker culture. Cheap parts, published projects and magazines or websites teaching how to use them is a pattern that continued through the microprocessor kits of the 1970s to modern development boards. The 2N-series general-purpose transistors that replaced the CK722 are still manufactured, and a student building a first amplifier on a breadboard is repeating, with a different part number, the same exercise.
Read Raytheon CK722 as the transistor that went to the workbench: not the best device of 1953 but the first to be priced, sold and written about for hobbyists, which seeded the practical skills of a generation.