Diodes

Diodes

• The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking it in the opposite direction (the reverse direction).
• As such, the diode can be viewed as an electronic version of a check valve. 
• c.f., check valve
• a valve that normally allows fluid (liquid or gas) to flow through it in only one direction
• This unidirectional behavior is called rectification, and is used to convert alternating current (ac) to direct current (dc).
• A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. 
• The reverse operation is performed by the inverter.
• Can have more complicated behavior than this simple on–off action, because of their nonlinear current-voltage characteristics
• e.g., diodes are used to regulate voltage (Zener diodes), to protect circuits from high voltage surges (avalanche diodes), to electronically tune radio and TV receivers (varactor diodes), to generate radio-frequency oscillations (tunnel diodes, Gunn diodes, IMPATT diodes), and to produce light (light-emitting diodes).