# The Semiconductor Diode

The semiconductor diode is the simplest semiconductor device and can be found in almost any electronic circuit. Diodes are manufactured with silicon (the most common) and germanium.

Diodes are composed of two parts, one called N and the other called P, which are separated by a barrier. This barrier has 0.3 volts in the germanium diode and approximately 0.6 volts in the silicon diode.

## Principle of operation of a diode

The N-type semiconductor has free electrons and the P-type semiconductor has free holes (absence of electrons). When a positive voltage is applied to the P-type semiconductor diode and a negative voltage to the N-type semiconductor diode, the electrons in the N side are pushed to the P side and the electrons flow through the material P beyong the limits of the semiconductor.

Likewise the holes in the material P are pushed, with a negative voltage, to the N side material and the holes run through the N material.

On the opposite side, when a positive voltage is applied to the N side and a negative to the P side, the electrons in the N side are pushed to the N side and the holes of the P side are pushed to the P side. In this case the electrons in the semiconductor don’t move and the electric current doesn´t run.

We can make the semiconductor diode work in 2 different ways:

## Forward bias

This is the case when the electric current circulates through the diode, following the path of the arrow (the arrow of the diode), or from anode to cathode. In this case the electric current passes through out the diode very easily behaving almost like a short circuit.

## Reverse bias

This is when the electric current in the diode wants to circulate on opposite direction of the arrow (the arrow of the diode), or from the cathode to the anode. In this case the electric current doesn’t run through the diode, and it behaves as an open circuit.

Note: The operation mentioned before refers to the ideal diode, meaning that we take the diode like a perfect element.

## Semiconductor diode applications

The diodes have many applications, but the most common one is the process of conversion from alternating current (A.C.) to continuous current (C.C.). In this case the diode is used like a rectifier diode.

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