Learn the basics of Electrical Engineering.

Basics of Diode

The diode is a two terminal component which allows the flow of AC in one direction and stops it in another direction.

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In this post you'll learn:

  1. What is diode and its physical design
  2. What is biasing of diode
  3. Practical applications

Physical design and circuit configuration of diode

Let's start our tutorial from the physical model of the diode. As explained earlier, it has two terminals, of which one is positive and another one is negative. The diode is black /carbon graphite in color. A silver colored line indicates the cathode (-ve terminal) of the component.

What is biasing of diode

Biasing is the method of applying dc voltages across the diode. As we know, the dc has two polarities, + ve and the negative. So we can use two biasing configurations, the first one is forward biasing and the second one is reverse biasing. During forward biasing the same terminals of both components are joined together and current is allowed to flow through the diode.

During reverse biasing, the opposite terminals of battery and diode are connected. i.e Positive (red) of the battery to negative of the diode and negative of the battery (black) to the positive of the diode. This condition completely stops the flow of current through the diode. Let's check how angry the diode is now:

Practical applications

The electricity coming to in our home outlets is AC in nature. The above-discussed behavior of diode is often employed to convert the alternating current (AC) to pulsating DC. During the positive cycle of alternating current, the diode allows the current to flow. During the negative cycle, there is no output and we can achieve the pulsating dc at the output.


  1. What is the purpose of connecting a diode in forward or reverse bias, in conclusion where do we found this connection though

    1. We can connect a diode in forward bias to allow the flow of current. And to stop the reversal flow of current. For example the laptopcircuitry contains a diode which allows current flow from wall outlet to laptop battery whereas it stops reverse current flow from battery to outlet under fault conditions.