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What is diode and types of diode?

Hello friends, in today’s post, we will know what is diode, their uses, the meaning of anode and cathode in diode, and the meaning of forward bias and reverse bias in the diode. And we will also talk about Types of diodes.

What is a diode?

what is diode and types

Diode is a kind of electronic device that allows current to flow in only one direction. It does not allow the current to flow in the other direction. It has two electrodes, one is named Cathode, and the other is named Anode. Diode is made up of semi-conductor.

What is Meaning of anode and cathode in diode?

In all diodes, you get to see two terminals. In this, one Anode is positive, and the other is the Cathode, the negative terminal.

cathode anode in diode

If you look at the diode, a white stripe is made on one side. The side with the white stripe is called the cathode terminal, meaning it is the negative terminal. Apart from this, the terminal on the other side is the Anode terminal means the positive terminal.

Where are diodes used?

Diodes are used in many devices. Such as rectifiers, signal limiters, voltage regulators, etc. Inside all these, you can easily see the diode installed, by the way, apart from this, there are many devices where diodes are installed.

Although diode is used in many places for different work, but if we talk about its main function, then it is used to convert AC current into DC current.

What is the bias in the diode?

There are two biases in a diode, both work according to the wiring. One is forward bias, and the other is reverse bias.

Forward bias: Current flows from positive to negative side inside the forward bias. That is, current flows from the anode terminal of the diode to the cathode terminal.

When we connect positive voltage to the anode and negative voltage to the cathode, at this time diode allows current to flow, and this is called forward bias.

Reverse bias: When the anode of the diode is connected to the negative voltage, and the cathode is connected to the positive. So it does not allow the current to flow forward; we call it reverse biasing. This is the exact opposite of forward bias.

Working principle of diode?

We can understand the working of the diode with the help of an example.

Example- We have a diode, two wires, a battery, and a led. We will connect the positive side of the battery with the diode’s anode with a wire’s help. Now we will connect the negative side of the battery to the LED and connect the other point of the LED to the cathode of the diode.
When connected in this way, the current will flow from the anode to the cathode. In this case, the diode will allow the current to pass through, and the LED will glow. We call this forward bias.

Forward bias Diode working

If we connect negative supply instead of positive supply to the anode of the diode and positive supply instead of negative supply to the cathode inside this connection, then the diode will not allow the current to flow.

Diode Reverse bias

And this process is also called reverse bias.

Types of diode?

Friends, although diodes can be divided in many ways depending on their use, but today I will tell you the names of about 23 diodes as well as some of their basic functions so that you can easily understand the working of any diode.
Friends, although diodes can be divided in many ways depending on their use, but today I will tell you the names of about 23 diodes as well as some of their basic functions so that you can easily understand the working of any diode.

1. Small signal diode By its name itself, we know that it is a diode running on small signals.

This diode is mainly used in that device in which the frequency is high, but the current is very low. such as radio etc. If we know the maximum current capacity of this diode, then it is only 150 mA, it can work only on very low current flow.

2. Large signal diode- This diode remains very heavily charged. You must have seen many times using diodes to convert AC to DC, usually large signal diodes are used there.
Large Signal Diode
This diode allows the forward current to pass through it and blocks the current when the current reverses. It is mostly seen inside the charging socket and inverter.

3. Zener Diode– This diode is a diode working on reverse bias. It is mostly used for voltage regulator.

Zener Diode

If we understand this by example- then suppose we have a charger which is giving us 12 volt supply. Now, if I want to run my 5 volt motor from this 12-volt supply, then at this time, I have to interrupt Zener diode will be needed. Because if I give 12 voltage to a motor running on 5 voltage, then that motor will get damaged. Zener Diode can control the supply from 1.2 volt to 200 voltage.

4. Avalanche diode- This diode also works on the reverse bias like the Zener diode.

Avalanche Diode

This works on the Avalanche breakdown principle. It is mainly used for RF Noise Generation and Microwave Frequency Generation.

5. TVS Diode (transient voltage supersession)- This diode is like a Zener diode, we use it for protection. This diode works to protect our circuit from the extreme voltage. Like in AC system, we use Fuse so that sometimes the value of current increases suddenly, then the fuse gives protection to our system.

In the same way, it also works to protect our system. This diode works to protect our circuit at any time when the voltage is too high.

6. Gunn diode- This diode work on negative resistance. It does not have P region, it has only N region.

Gunn Diode

Due to the N region in this diode, whenever the voltage in the circuit increases, the current also increases, but after reaching a certain level, it again suddenly drops the current, that is why it is also called transferred electrons device. It is mainly seen inside Microwave RF Device.

7. LED (Light Emitting Diode)- Light emitting diode is such a diode inside which light burns when current flows. This happens because the particles (electrons and holes) carrying its current get combined with each other.

LED Light Emitting Diode

Due to this layer, a heavy laser takes out. It is mostly used inside CD, Laser Light, and Blu-ray.

8. Laser diode- This diode works like a LED diode. Just inside it, a reflection layer is placed in the middle of the P N junction, which is also called I layer.

Laser Diode

The laser Diode emits a heavy laser because of this layer. It is mostly used inside CD, Laser Light and Blu-ray.

9. Constant current diode- All the diodes we have known so far were controlling the voltage, but this diode works to control the current.

Constant Current Diode

It allows the current to pass through to a specific value, after which it blocks the rest of the current. Meaning this diode allows only limited current to flow.

10. Varactor diode This varactor diode works like our variable capacitor. As we know that capacitor works blocking DC to advance AC.

Varactor Diode

There are three layers inside it, there is one more layer with p n. The third layer is the heavily doped layer of the N layer. With the help of this, we can change the voltage inside the circuit and send it. It is mostly used inside satellite and cell phones.

11. Schottky Diode- This diode is used in high frequency and digital applications. Its switching speed is quite fast.

Schottky Diode

There is no P N junction in this. In its place, there is a bond of lightly and heavily doped metal. It is sometimes used to protect the transistor or to give protection against reverse current.

12. Super barrier diode- This diode is an advanced version of the Schottky diode.

Super Barrier Diode

There is still more research going on on this. It works as rectifier. It also works to convert AC to DC. It can also switch itself quite fast.

13. Shockley diode- This diode is a very rarely used. This P N P N is a diode made up of four junctions, its junctions are alternate to each other.

Shockley diode

It is like a thyristor without gate. Although its use has stopped today, instead of it SCR is used.

14. Step recovery diode- This is a semi junction diode.

Step Recovery Diode

It is also called snap off diode and charge storage diode. This is mostly seen inside microwave and parametric amplifiers.

15. PIN Diode- This is an improved version of P N junctions diodes.

PIN Diode

PIN Diode has an intrinsic layer between P and N layer inside it, which we also call I layer, I layer is a layer without charge. This is mostly seen inside photo detectors and RF switches.

16. Tunnel diode- This diode works as high-speed switching. It does the switching in a few nanoseconds.

Tunnel Diode

Tunnel diode The depletion region in the middle of the PN junction of this diode is very less. Therefore, the current passes through it very quickly, and the switching is also fast. This is mainly seen in microwave circuits.

17. Photo Diode- This diode is a reverse bias diode.

Photo Diode

It does not allow current to flow in normal conditions. When any light falls on it, then it allows the current to flow. It is a kind of light detector.

18. Gold doped diode- In these diodes, gold is used for dopant, due to this, it allows very little leakage current in reverse bias. Due to it being of gold, it works very fast. It works very well on signal frequency only.

19. Crystal diode- This diode is a diode used in receiver and detector.

Crystal diode

This point contact device is like a diode.

20. Vacuum diode There are two electrodes inside it, which act as cathode and anode.

Vacuum diode

Vacuum diode in this cathode is made of tungsten.

21. Peltier diode- This diode sensor acts as a heat engine for thermo electric cooling. There are two wires in it, one is positive wire and the other is negative wire.

Peltier Diode

It is mostly used in heating and cooling applications. This diode is also known as Thermo Electrical Diode in many places.

22. SCR Diode (Silicon controlled rectifier)- This diode is a type of thyristor.


There are three terminals inside this diode – cathode, anode and gate. It allows current to flow only when the diode gate is triggered.

23. Point contact devices diode- In this diode gold or tungsten wire is used to form PN junction region as point contact by flowing high electric current.

Point contact devices diode

Point contact devices diode The end of this diode has an N followed by gold or tungsten wire. The type remains germanium which allows the signal to go in normal condition but acts as an insulator in reverse condition.

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