Introduction to Diode

Diode is a two terminal electrical component i.e. anode and cathode. Diode is the first semiconductor electronic component, it is an very important component in electronics, we can say that  " Diode is the Heart of Electronics".
Types of Diode include Rectifier diode(normal diode), Zener diode, Signal diode, Light emitting Diode etc.

Construction of Diode

Diode is made up of two semiconductor material (p-type and n-type material, this semiconductors are not in pure type.
P-type and N-type semiconductors are obtained by adding some impurities to them in definite proportion. This process is known as Doping
P-type and N-type material are joined together to form a diode, thus in diode P-type semiconductor is slightly more doped than N-type semiconductor.
In diode P side is known as Anode and N side is known as cathode.

Construction and Symbol of Diode

Function of Diode
Diode allow the electricity to flow only in one direction.The arrow of the circuit symbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves.
i.e. if we connect anode of the diode with positive terminal of battery and cathode with negative terminal, then the current will flow in the circuit. but if we connect diode anode with negative terminal of battery and cathode with positive terminal, then diode will act as open circuit and no current will flow in the circuit.
For example see the below circuits,

 

Forward Voltage Drop               

 Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the forward voltage drop and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic.








Reverse Voltage

When a reverse voltage is applied, a perfect diode does not conduct, but all real diodes leak a very tiny current of a few μA or less. This can be ignored in most circuits because it will be very much smaller than the current flowing in the forward direction. However, all diodes have a maximum reverse voltage (usually 50V or more) and if this is exceeded the diode will fail and pass a large current in the reverse direction, this is called breakdown.




There are various application of Diodes  such as Rectifier, protection diodes for relays and circuits etc.
Transistor are also made up of diodes, when two diodes are joined together they form a type of transistor.