Newnes Audio and Hi-Fi Engineer's Pocket Book, 3rd Edition

198

Audio transistors

Point contact The earliest device known as a transfer

resistor (transistor) consisted of two fine metal points in close

proximity on a semiconductor material having a deficiency of

free electrons (P material). Current injected into the material

via the one point, termed the emitter, released a larger current

gathered by the other, the collector. The closer together the

points were, the larger the current gain.

A later version, easier to manufacture, had cavities etched

on opposite sides of the germanium base material with tiny jets

of hydrofluoric acid into which the metal contacts fitted.

Spacing was thus the thicknes ...