Introduction to diodes

Diodes are often overlooked by the general public because they dwell inside the inner workings of electrical devices. Along with many other components in an electrical circuit, diodes help circuits perform tasks that circuits were designed to do. Some diodes are even useful without its fellow components, such as the light emitting diode, or LED, which emits photons when activated. To find out more on what diodes are used in, click on the Uses of DIODES link on the left.

A light emitting diode
How Stuff Works

Diodes are typically made of one or two elements. When placed in a circuit, a diode can either allow current to flow through it or prevent current from flowing through it. Its behavior depends on the amount of voltage fed through the diode and/or the orientation of the voltage source. In most cases a diode will not deliver current through it until a certain voltage range is applied to it. To know more about the anatomy of a diode, click on the Physics of DIODES link on the left.

There are many different types of diodes, each type created to allow current to pass through it when certain criteria is met. This website will mainly focus on diodes discussed in introductory electrical engineering courses: the junction diode, zener diode, light emitting diode, and the photodiode.

Georgia State University's "Hyperphysics" website

The diagram on the left shows the symbols representing some types of diodes. These symbols are used in schematics of circuits for design purposes. Notice that each symbol has a common shape: the triangle. The triangle is the ideal shape to represent a diode because the diode has a negative end (cathode, or the triangle's pointy end) and a positive end (anode, or the triangle's wide end). A diode's orientation in a circuit is crucial, as its orientation determines whether current is allowed to go through the diode or not.