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Introduction to Diodes

Diodes are polarised, which means that they must be inserted into the PCB the correct way round.
This is because an electric current will only flow through them in one direction (like air will only flow one way through a tyre valve).

Diodes have two connections, an anode and a cathode. The cathode is always identified by a dot, ring or some other mark.

Diodes Symbols Diagram

The pcb is often marked with a + sign for the cathode end.

Diodes come in all shapes and sizes. They are often marked with a type number. Detailed characteristics of a diode can be found by looking up the type number in a data book.

If you know how to measure resistance with a meter then test some diodes. A good one has low resistance in one direction and high in the other.

There are specialised types of diode available such as the zener and light emitting diode (LED).

Diodes Symbols Diagram

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