Sam Newman 10E        

The Symbol for a basic diode is:        

The Symbol for an LED is:                

A diode is an electronic device that permits current flow  in only one direction. Most diodes are semiconductors.

A diode has a low resistance to electric current in one direction and a high resistance to it in the reverse direction. This makes a diode useful as a rectifier, which can convert alternating current (AC) into direct current (DC).

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A diode using this property is called a Zener diode. It can be used to regulate the voltage in a circuit. Semiconductor diodes can be designed to have different characteristics.

A varactor diode has a capacitance that is dependent upon the voltage across it.

In another kind, the tunnel diode, the current through the device decreases as the voltage is increased within a certain range. This is called negative resistance and it is useful as an amplifier.

Light-sensitive or photosensitive diodes can be used to measure illumination as the voltage drop across them depends on the ...

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