A diode is a two-terminal semiconductor component that lets electric current flow in one direction only. It has two terminals: the anode and the cathode.
When voltage is applied in the “forward” direction (anode more positive than cathode) and exceeds a small threshold (typically around 0.7V for silicon diodes) the diode conducts and current flows freely. Applied in reverse, the diode blocks current almost entirely, acting like an open switch.
You can imagine corridor with a gate (see below). If you walk from left to right (= from Plus to Minus – the direction of the diode, you can walk through the gate – it opens in that direction. If you would walk from right to left (= from Minus to Plus, oposite direction diode), the gate does not open and you cannot pass. The positive side is called the Anode and negative (minus) side is called the Cathode.
Common field of application:
Rectification (converting AC to DC), protecting circuits from reverse polarity, signal demodulation, and voltage regulation (via specialized types like Zener diodes) and light emission (LEDs).
Symbols of the diode:
