Diode

Standard circuit symbols: Cell; Battery; Open switch; Lamp; Fuse; Ammeter; Voltmeter; Resistor; Variable resistor; Thermistor; LDR; Diode; LED. Resistors and related components use the European rectangular style.

A diode behaves like a one-way electrical valve. In the forward direction, very little current flows at first; after the forward potential difference becomes sufficiently large, the current rises very rapidly. Its resistance has become much lower in this conducting region.

By convention, conventional current is treated as leaving the positive terminal, passing through the external circuit and returning to the negative terminal. This convention is useful when deciding whether a diode is facing the conducting direction.