Definition
An electronic device which consists of two terminals (anode,
cathode) and conducts when it is forward biased is called Diode
or Rectifier.
Symbol
Types
A diode is used in a wide variety of electronic circuits
with its various types and workings. The most commonly used types are as under:
- Light Emitting Diode
(LED)
- Avalanche Diode
- Laser Diode
- Schottky Diodes
- Zener Diode
- Photo Diode
- Varactor Diode
- Rectifier Diode
- Small Signal Diode
- Large Signal Diode
- Super barrier Diode
- Peltier Diode
- Gunn Diode
- Crystal Diode
- Silicon controlled
Rectifier
- Vacuum Diodes
Rectification
A diode is also called a rectifier because it
converts AC supply into DC supply. Diode is also used in DC
supplies to convert AC into DC. A single diode converts a very
small amount of AC into DC that is why so many diodes are used in High
power DC Supplies.
Construction
It is a two terminal device consists of P type and N
type materials and have one PN junction. It is made up two materials
Silicon and Germanium. The P type region is referred to as
anode and the N type region is referred to as cathode.
Working
When the diode is in forward biased, its start
conducting and acts like a conductor. On the other hand when diode is reverse
biased, it acts like an insulator in the beginning and after
increasing the reverse voltage a huge amount of current increases rapidly
at its maximum value. If the reverse voltage are increased more than the diode
will destroy.
Diode
Biasing
Diode biasing is the scheme of connecting an electric current to a diode
with two different methods. In these methods only battery terminals are
replaced or a diode is replaced in a circuit. These two methods named as
Forward Bias and Reverse Bias.
Forward Bias
In forward bias, the anode is connected to the
positive terminal of the battery whereas the cathode is connected
to negative terminal of the battery. The diodes cannot conduct in start and
after increasing the voltage from its internal barrier voltage (0.3v in case of
silicon or 0.7v in case of germanium) the diode start conducting and current
flows through it.
Reverse Bias
In reverse bias, the anode terminal of the diode is
connected to the negative terminal of the battery whereas the cathode is
connected to the positive terminal of the battery. In reverse bias
connections, Majority carriers blocked and small amount of current flows
through the diode. When the reverse bias voltage increases, the reverse
current increases very quickly and reaches at its maximum value.
VI Curve
The following is the VI curve of the diode:
Applications
Diodes are widely used as Rectifiers, Clipping Circuits, Clamping
Circuits, Logic Gates, Voltage Multiplier Circuits, Reverse
Current Protection and in Solar Panels.