A diode is an electronic component that conducts electrical current in one direction and blocks current in the opposite direction. Each diode contains two electrodes: the anode and the cathode. Most diodes are constructed with semiconductor materials, though some contain metal or pure elemental gas in the electrodes. Uses for diodes include rectifier, signal limiter, voltage regulator, switch, signal modulator, mixer or demodulator, and oscillators. The energy of a diode is measured by forward voltage drop, or a decrease in voltage along the diode when carrying current.
The silicon diode is the least expensive to buy and the most common diode. These diodes have a forward voltage drop of 0.65 volts.
The germanium diode uses a germanium crystal pellet as the rectifying element, the property that causes energy in a diode to flow in only one direction. Germanium diodes have a forward voltage drop of approximately 0.1 volt. These diodes are higher in cost than silicon diodes.
The Zener diode has a specific reverse breakdown voltage, the minimum voltage required to cause the diode to conduct in reverse. Zener diodes are used as switches. They are also used in conjunction with a current-limiting resistor to regulate voltage.
When P-type and N-type semiconductors are joined together, it forms a P-N junction. Photodiodes are P-N junctions that are highly light sensitive. They are used to convert solar energy to direct current as either a solar cell or a photovoltaic.
Light-emitting diodes, LEDs, are constructed from semiconductor material that increase light output. LEDs burn out only if the current limit of the diode is surpassed. In order to keep an LED intact, it is used with a resistor. LED diodes can also be used as photodiodes.
A flashing LED works the same way as a standard LED, but contains a microcircuit that allows it to flash. Flashing LEDs draw current when they flash. Because of this, they are used to power timing-dependent circuits. Flashing LEDs, like standard LEDs, are light sensitive. The brighter the light surrounding the flashing LED, the faster the flash.