Diodes

A diode is an electrical component that only allows electricity to flow in one direction. The material used to make a diode is usually a semiconductor such as silicon. The reason that a diode can block electricity in one direction and conduct it in the other is because of the p-n junction that is formed by the silicon semiconductor. The p-n junction is a boundary that is formed between a piece of p-type silicon and n-type silicon. The 'p' in the p-type semiconductor represents the fact that it is positively polarized, the same can be said for the n-type in which the 'n' indicates that the semiconductor is negative. Both the p-type and n-type semiconductors have aproximately the same level of conductivity.

The side of the diode that is connected to the p-type semiconductor is known as the anode. The anode is the negative side of any electrical device, on a diode this side is usually marked by a white line. The complete opposite can be said for the side of the diode connected to the n-type semiconductor which is known as the cathode. The cathode is the positive side of any electrical device.

Depending on the voltages of the two semiconductor regions the junction between the two semiconductors can become depleted of charge carriers. Once the carriers are depleted the semiconductor will no longer conduct electricity. This property is described as either forward bias and reverse bias. Bias in a semiconductor is the applied voltage to the p–n junction. When no current is passing through the diode the electrons in the p-n junction return to a state of equilibrium. That means that that all of the electrons return to the p-type side of the junction and all of the holes return to the n-type side. Holes are the conceptual and mathematical opposite of an electron.