Diodes

A diode is a device through which current (a flow of positive charge) flows in one direction only. The symbol for a diode...

... is a stylized diagram of a point-contact diode - a fine pointed phosphor bronze (etc.) wire bonded to the surface of a semiconductor. The forerunner of the modern point-contact diode was the unreliable 'cat's-whisker', the bane of early radio operators. A cat's-whisker diode can be made with a needle and a blue Gillette blade. A cat's-whisker diode is unreliable, and must be frequently repositioned.

Diodes are of several types, including:-

1 ... Point contact diodes (evaporated metal version).

2 ... Oxide layers.

2 ... p-n junctions.

3 ... Vacuum tubes.

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