Definition:
"Diode is an electrical component which allow the current to flow in one direction."
Explanation:
Diode is use to flow the current only in one direction and to block the current, if it flows in other direction. This property of blocking current in one direction and allowing it in only one direction is due to its construction which is explain below. It does not change the current, it just block the current to flow in other direction in a circuit. It is also use to convert AC source into DC source.
By blocking the negative interval and allowing only positive interval and by using some filter, decreases the fluctuation.
Construction:-
The diode is made up by the junction of two semiconductor of same material, lets suppose Silicon (Germanium could also be used). One semiconductor is doped with p type material which is boron and other semiconductor with n type material which is phosphorus. This junction is known as P-N junction.
In P there is holes which is majority charge and in N there is electrons which is majority charge.
When we make junction of these (p-type and n-type) then holes which are majority charges in P, moves towards the N, and combine with the electrons, and majority charges in
N which are electrons moves towards the P junction and combine with the holes.
During this process there form a junction which is known as PN junction. Which consists both holes and electrons. And no more transfer of electrons and holes occurs(because of this junction wall.).
Working:
In electric Circuit, we take symbol for diode is,
There are bias (applying any source) condition for semiconductor diode. Forward bias and Reverse bias. Diode works only in forward bias. In reverse bias, it blocks the flow of current in circuit or in other words. It becomes open circuit. which is its main property to allow current in only in one direction.
how to forward bias the diode?
We could do it by connecting positive terminal of voltage source from the anode and negative terminal with the cathode. And for reverse bias its vice versa.
How it allows current to flow in forward bias?
It allows current to flow in forward bias, because we connect positive terminal of voltage source with anode and it attracts electron from the N type. So electrons start to flow towards the anode terminal. And there is junction wall between diode, so to overcome there needs voltage of 0.3 or 0.7 . so could say that it is diode starting voltage.
How it blocks current in reverse bias?
It blocks current in reverse bias, because the positive terminal of voltage source is connected with the cathode so it attracts electron towards cathode terminal so because of it, negative electrons from P type and positive holes from N type goes into junction and increases it. so junction widens and blocks the transfer.
