These diodes are the normal PN junction diodes, which allow current to flow through them in only one direction and stop in the other direction. These diodes are used in rectifier circuits to convert alternating current into direct current.

In the above figure, we can see the same rectifier diodes with a metal projection. This is added to the diode to minimize the heat distribution which might affect the diode sometimes. Such a metal projection is called as Heat sink. These help in the improvement of the diode performance and the diodes will be able to withstand high powers, without getting affected.

There are circuits such as Half wave rectifier and Full wave rectifiercircuits which use these diodes. These circuits are discussed in ELECTRONIC CIRCUITS tutorial. These rectifier circuits are used in Power supply sections of many circuits where alternating input current has to be converted into direct current for that circuit applications.