Circuit Design: Know It All

Chapter 2

The Semiconductor Diode

Ian Hickman

The semiconductor diode, like its predecessor the thermionic diode, conducts current in one direction only. It is arguable that diodes in general are not really active devices at all, but simply nonlinear passive devices. The earliest semiconductor diode was a point contact device and was already in use before the First World War, being quite possibly contemporary with the earliest thermionic diodes. It consisted of a sharp pointed piece of springy wire (the “cat’s whisker”) pressed against a lump of mineral (the “crystal”), usually Galena, an ore containing sulfide of lead. The crystal detector was widely employed as the detector in the crystal sets that were popular in the early days of broadcasting. ...