Rectifier Diode

A rectifier diode is a semiconductor device used to convert alternating current into direct current.The most important characteristic of a diode is unidirectional conductivity.In a circuit, current can only flow from the anode to the cathode.It generally contains a PN junction with two terminals: anode and cathode, and its structure is shown in the figure.

 

The carriers in the P-region are holes, and those in the N-region are electrons, forming a potential barrier between the P-region and N-region.When an external voltage is applied with the P-region positive relative to the N-region, the potential barrier is lowered, and stored carriers are generated near both sides of the barrier, allowing large current flow with a low voltage drop (typically 0.7V). This is called the forward conducting state.

 

If a reverse voltage is applied, the potential barrier increases, enabling the diode to withstand high reverse voltage with only a very small reverse current (called reverse leakage current) flowing through it. This is called the reverse blocking state.

 

Rectifier diodes exhibit obvious unidirectional conductivity.They can be made of semiconductor materials such as germanium or silicon.Silicon rectifier diodes feature high breakdown voltage, low reverse leakage current, and excellent high-temperature performance.

 

Generally, high-voltage and high-power rectifier diodes are made of high-purity monocrystalline silicon (heavy doping tends to cause reverse breakdown).These devices have a large junction area and can carry relatively high currents (up to thousands of amperes), but their operating frequency is not high, generally below several tens of kilohertz.

 

Rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits.To achieve full-wave rectification, they must be connected to form a rectifier bridge.