A diode is an electronic component that allows current to flow primarily in one direction. It has low resistance in one direction and high resistance in the other direction. A diode is also known as a rectifier because it changes alternating current (AC) into pulsating direct current (DC) . The most commonly used type of diode today is a semiconductor diode, which is a crystalline piece of semiconductor material with a p-n junction connected to two electrical terminals. When the anode voltage is more positive than the cathode voltage, the diode is forward-biased and conducts readily with a relatively low-voltage drop. When the cathode voltage is more positive than the anode, the diode is reverse-biased and acts as an insulator, not permitting current to flow.
Diodes are assigned current ratings, and if the rating is exceeded and the diode fails, it may short and either allow current to flow in both directions or halt current from flowing in either direction. There are different types of diodes, including signal diodes, rectifier diodes, and Zener diodes. Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices, and they are usually reverse-biased (non-conducting) under normal circumstances. When the voltage rises above the normal range, the diodes become forward-biased (conducting) .
