Diode: A diode is a two-terminal electronic component that has a low resistance to the flow of current in one direction thus allowing the passage of current in one direction whereas a high resistance in the other, thus restricting the flow of current in that direction. Semiconductor diodes are two terminal devices that consist of a p-n junction and metallic contacts at their two ends.
A p-n junction is denoted by the symbol shown. Here, the direction of the arrow indicates the permissible direction of the current.
Semiconductor Diode: A semiconductor diode is basically a p-n junction diode. It is a two terminal device which conducts current only in one direction.
The above figure represents the symbol for p-n junction diode which symbolizes the direction of the current. By applying an external voltage V we can vary the potential barrier.
Diodes may be considered to be in two states when in a closed circuit:
Forward Biased: This simply means that the diode is arranged in the direction of the current. Hence the current flows from positive to negative part inside the diode.
Reversed Biased: This term denotes that the diode is arranged in a manner so that the conventional current, if it were possible, should move from negative part of diode to positive part. However, as it is not possible, practically no current flows in this situation.