Diodes, one-way current conductors, are used for voltage regulation, AC/DC conversion, and circuit protection. Forward-biased at 0.6V, conduct current, reverse bias blocks it.

The four-layer diode was the key to William Shockley's plan to revolutionize AT&T's phone system. It was a great device in theory, but not in practice -- at least not at the time when Shockley ...