What Is Diode | How Diode Works | Uses of Diode

Introduction

We're going to be looking at diodes to understand the basics of how they work as well as where and why we use them.

What is Diode:

So what is a diode, a diode looks something like this and it comes in different sizes.

Figure 1: How Diode Looks Like Externally

They typically have a black cylindrical body as a stripe at one end as well as some leads coming out to allow us to connect it into the circuit. One end is known as the anode and another end is the cathode as shown above. You can also get other forms such as the Zener diode or an LED which is a light-emitting diode, but we're not going to cover those in this blog. 

A diode allows current to flow in only one direction in a circuit. If we imagine a water pipe or the swing valve installed as water flows through the pipe, it will push open the swing gate and continue to flow through.

Figure 2: Diode Water Pump Analogy

However, if the water changes the direction the water will push the gate shut and it will prevent it from flowing therefore the water can only flow in one direction as shown in the image above. This is very similar to a diode we use them to control the direction of current in a circuit.

We have noticed that the electrons flow from the negative to the positive terminal. However, you might be used to seeing conventional flow which is traditional in electronics engineering and this is where the electrons flow from the positive to the negative electron flow is what's actually occurring but you might come across conventional current still as these explanations are easier to understand just be aware of the two on which one we're using.

Figure 3: Diode and LED Forward and Reversed Connection

So if we connect a diode into a simple led circuit like this one, we see that the LED will only turn on when the diode is installed the correct way and that's because it allows current to flow in only one direction.

So depending on which way the diode is installed this will act as either a conductor or an insulator. In order for the diode to acts as a conductor, the stripe end is connected to the negative, and the black end is connected to the positive this allows the current to flow. We call this the forward bias. If we flip the diode it will act as an initiator and the current can't flow and we call this the reverse bias.

How Does The Diode Works

So how does the diode work as you may know electricity is the flow of free electrons, but atoms we use copper wires because copper has a lot of free electrons which makes it very easy to pass electricity through we use rubber to insulate the copper wires and keep us safe because rubber acts as an insulator which means its electrons are held very tightly and they can't, therefore, move between other atoms.

If we look at the basic model of an atom for a metal conductor. We have the nucleus at the center and this is surrounded by a number of orbital shells which hold the electrons each shell holds a maximum number of electrons an electron has to have a certain amount of energy to be accepted into each shell the electrons located far east away from the nucleus hold the most energy the outermost shell is known as the valence shell and a conductor has between 1 and 3 electrons in its valence.

Figure 4: Copper Cu Electronics Model

Shell the electrons are held in place by the nucleus, but there's another shell known as the conduction band.

If an electron can reach this then it can break free from the atom and move to another with methyl atoms such as copper the conduction band and the valence shell overlap. So is very easy for the electron to move with an insulator. The outermost shell is packed. There's very little to no room for an electron to join the nucleus has a tight grip on the electrons and the conduction band is far away.

So electrons can't reach this to escape therefore electricity cannot flow through this material. However, there's another material known as a semiconductor silicon is an example of a semiconductor with this material. 

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