Diode is the simplest electronic components with only one PN junction.
Diode has two electrodes: anode and cathode. Having one PN junction, diode is highly non-linear component with capability of conducting current in only one direction. This feature is called rectification. Ohm’s law is not applicable to the diode.
I-V characteristic of common diode is given in figure bellow.
If diode is forward biased, and voltage is higher then threshold voltage, current grows exponentially with respect to diode voltage. Threshold voltage is usually 0.5-0.6V for silicon diodes, and 0.2V for Schottky diodes. Due to steep characteristic, it is very helpful to model forward bias diode as ideal voltage generator with voltage of 0.6V-0.7V for silicon diodes, and 0.3V for Schottky diodes.
Since diode conducting current in only one direction, diodes are widely used for converting alternating current into direct current (in diode bridge for example). Such diodes operate in forward biased region while conducting and in inverse biased region while cutting off negative voltage from the load. Most common diodes for this purpose are:
Some types of the diodes are designed to operate exclusively in inverse biased region of I-V characteristic. These are:
Some other types are designed to operate exclusively in forward biased region, such as:
Even though all the diodes consist of just one PN junction, depending of technology and applied materials, there are many different types of diodes which are used for different purposes. Diode application schemes supported in this site are: