The primary transistors have been level contact units, not removed from the cats-whiskers of early radio receivers. They have been fragile and costly, and their efficiency was not very excessive. The transistor which introduced the units to a mass viewers by the Fifties and Sixties was the one which adopted, the alloy diffusion kind. [Play With Junk] has a failed OC71 PNP alloy diffusion transistor, first launched in 1957, and has cracked it open for a more in-depth look.
Contained in the glass tube is a small wafer of germanium crystal, surrounded by silicone grease. It varieties the N-type base of the system, with the collector and emitter being small indium beads fused into the germanium. The junctions have been fashioned by the ensuing area of germanium/indium alloy. The surface of the tube is pained black as a result of the system is light-sensitive, certainly a model of this transistor with out the paint was bought because the OCP71 phototransistor.
These units have been leaky and noisy, with a low most frequency and low acquire. However they have been dependable and finally reasonably priced, so a few of us even reduce our digital enamel on them.
