Diodes have numerous applications across the electronic industry,
and they are an integral part of any electronic device.
In this video, we will explore the inner workings and applications of the diode in great detail.
Basically, a diode is a one-way valve for electricity.
Let's take a look at the internal structure of a diode.
The diode is made of a semiconductor such as silicon.
Pure silicon does not have any free electrons,
but the silicon used here is not pure: one part is doped with n-type impurity
and the other part is doped with p-type impurity.
So at the n-side of the diode we will have free electrons, and at the p-side,
we will have vacant positions for electrons.
Something very interesting happens at the p-n junction of the diode.
The abundant electrons on the n-side have a natural tendency to migrate to the holes
that are available on the p-side, so the p-side boundary is slightly negatively charged,
and the n-side boundary is slightly positively charged.
You can see the depletion region that is created.
The resulting electric field will oppose any further natural migration of electrons.
In short, it builds a potential barrier for electron flow.
If you apply an external power source across the diode as shown,
the power source will attract the electrons and holes
Electricity flow is impossible in this case.
This condition is known as reverse bias of the diode.
You can see that the width of the depletion region increases here.
However, if you connect positive terminal of the power source to the p-side of the diode,
the situation is quite different.
Assume that the power source has enough voltage to overcome the barrier potential.
You can immediately see that the electrons will be pushed away by the negative terminal.
When the electrons cross the potential barrier, they will be drained of energy,
and will easily occupy the holes in the p-region.
But due to the attraction of the positive terminal,
these electrons can now jump to the holes nearby in the p-region,
and flow through the external circuit.
This is known as the forward biasing of a diode.
Simply put, a diode acts like a one-way valve for the flow of electricity.
Now, let's vary the input voltage and study the diode's response to it.
In reverse voltage, as explained, you can observe a negligible electricity flow.
In the forward condition, up to 0.7 volt, you will find a negligible electricity flow.
But right after crossing this barrier potential value,
there will be a steep increase in the current flow.
However, you can note that voltage across the diode does not go much higher than 0.7 volts,
even with high input voltage.
This is due to n forward-biased condition.
The diode offers very low resistance against the current flow.
At the reverse biased side, applying a very high voltage will damage normal diodes
and result in a high current flow.
The one-way electricity flow that is characteristic of the diode leads to interesting applications
like a bridge rectifier.
During the positive half, the circuit will conduct as shown.
The other two diodes will be in a reverse biased state.
During the negative half, the reverse will be the case.
So we will get the same current flow direction at the output.
We can further smooth this output by introducing a capacitive filter and regulator.
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