Diodes

A diode is a two terminal electronic component that conducts current in only one direction. Vacuum tube diodes have been made for over a century. Today, semiconductor diodes are the norm.

Semiconductor Diodes

A semiconductor diode is a PN junction with a terminal on each side to allow a connection to the material. Inside the diode, the terminal that electrons flow toward, when the diode is conducting, is called the anode. The terminal that electrons flow away from is called the cathode. Conventional current flows from anode to cathode.

The schematic symbol for the diode looks like an arrow touching a straight line.

Diode symbol and package

When forward biased conventional current flows in the direction of this arrow. The cathode is the straight line and the anode is the back of the arrow. A diode package has a band painted on one end. The cathode is the side with the band. Therefore, a diode will be forward biased when the more positive voltage is connected to the terminal opposite to the end with the band and the more negative voltage is connected to the terminal at the end with the band. Typically, a silicon diode is considered to be forward biased when the voltage at the anode is 0.7V more positive than the voltage at the cathode.


How Diodes Work