Q. WHAT IS DIODE ?
A diode is a semiconductor device that essentially acts as a one-way switch for current. It allows current to flow easily in one direction, but severely restricts current from flowing in the opposite direction.
Diodes are also known as rectifiers because they change alternating current (ac) into pulsating direct current (dc).
Diodes have polarity, determined by an anode(positive lead) and cathode (negative lead).
When a diode allows current flow, it is forward-biased. When a diode is reverse-biased, it acts as an insulator and does not permit current to flow.
Forward Biased Diode

When a diode allows current flow, it is forward-biased. When a diode is reverse-biased, it acts as an insulator and does not permit current to flow.
Forward Biased Diode

positive terminal of a source is connected to the p-type side, and the negative terminal of the source is connected to the n-type side, the diode is said to be in forward biased condition.
In this stage diode allows current flow.
This is because in this condition the depilation layer of the junction is very thin and week , and provides very low resistance to flow of electron as the voltage increases this depilation layer is breaked down and current start following .
Reverse Biased Diode
In this stage diode allows current flow.
This is because in this condition the depilation layer of the junction is very thin and week , and provides very low resistance to flow of electron as the voltage increases this depilation layer is breaked down and current start following .
Reverse Biased Diode

Now if the diode is reverse biased i.e. positive terminal of the source is connected to the n-type end, and the negative terminal of the source is connected to the p-type end of the diode
there will be no current through the diode except reverse saturation current. This is because at the reverse biased condition the depilation layer of the junction becomes wider with increasing reverse biased voltage. Although there is a tiny current flowing from n-type end to p-type end in the diode due to minority carriers.
Now if reverse applied voltage across the diode is continually increased, then after certain applied voltage the depletion layer will destroy which will cause a huge reverse current to flow through the diode. If this current is not externally limited and it reaches beyond the safe value, the diode may be permanently destroyed..
there will be no current through the diode except reverse saturation current. This is because at the reverse biased condition the depilation layer of the junction becomes wider with increasing reverse biased voltage. Although there is a tiny current flowing from n-type end to p-type end in the diode due to minority carriers.
Now if reverse applied voltage across the diode is continually increased, then after certain applied voltage the depletion layer will destroy which will cause a huge reverse current to flow through the diode. If this current is not externally limited and it reaches beyond the safe value, the diode may be permanently destroyed..
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