Diode: An Important Electronic Component: Today I have chosen this topic because many friends want me to make an article about electronic components as well.I often write articles related to telecom. But now taking care of all reader friends, I will also write about electronic components. Today I am writing about diode, if there is any deficiency, then you will definitely give your suggestions. The diode is one of the many components used in electronic circuit. A diode is a device that conducts in one direction only.
diode is a semi conductor device and this conducts in one direction only. It has two terminal. The silver color line in the diode is the terminal  called cathode (symbol of the diode the tip of the triangle is the cathode) and the anode on the other side.Current following through diode in a direction in the cathode and anode, there is a Zero Resistance, and there is very high resistance in the other direction, causing the Current Flow to become zero.


A lady engineer working on diode electronic circuit
Diode Details

What is Diode

Diode is a very important electronic component widely used in electronic circuit.A diode is very special type of electronic component that has two electrodes called anode and cathode. Most diode (semiconductor material) are made of semiconductor material such as silicon, germanium, or selenium. Diode are smaller in shape and size but it has larger function. Generally diodes used as rectifiers, signal limiters, voltage regulators, switches, signal modulators, signal mixers, signal demodulators and oscillators.

Normally the diode allows the electric current to move in only one direction. When the cathode of the diode connects the terminal to the negative voltage and the anode to the positive voltage, current starts flowing through it and this is called forward bias.And when we connect the anode of the diode to the negative voltage, it does not allow the voltage to go forward which we call reverse biasing and even if we connect the cathode to positive it does not let the voltage go.
Image of diode working unidirectional only
Diode working unidirectional

For example, look at the circuit diagram above which has a battery,diode and lamp/bulb.Two terminal semiconductor diode device used in above circuit. look how diode has a very important property of conducting in one direction.

In above figure, battery,diode,small lamp all are connected in series,when diode are connected in this manner the lamp glows.It means diode is conducting and current is flowing in the circuit.

In other figure terminal of diode are reversed, when diode is connected in this manner the lamp does not glow. It means current is not flowing in the circuit.Diode does not permit the current to flow.

Symbol of Diode

symbol of diode used in electronic circuit
Diode symbol


There are several types of diodes, which I will write ahead in the same article, but generally the diode symbol is given below.As you all know there are many types of diode, so the symbols of all of them are also different. And these symbols are used to create a circuit diagram where it is shown that it is a diode and what value it is.

And in the photo above, you can see that the diode is cylindrical and has a white strip on one side. This means that is the terminal called cathode on this side.

Semiconductor Materials for the Diode

We all are very well familiar with conducting and insulating materials. Conducting materials are good conductor of electricity like-copper,silver,aluminium etc. Insulating materials are bad conductor of electricity like- porcelain,glass,quartz,rubber etc.

Another group of materials such as germanium and silicon,these are neither good conductor nor good insulator. At room temperature these materials have conductivity considerably lower than that of conductors,but much higher than that of insulators. For this reason that these materials are called the semiconductor.

Semiconductors have another very important property . The conductivity of a semiconductor can be changed to a very large extent,by adding a very small amount of some specific materials that called impurities. The main semiconductor materials are germanium and silicon.In this article it is not appropriate to explain more about semiconductor materials, so now I
 am going to explain below the type of diode.

Types of Diode

The diode are placed in different categories according to their work. All the diode have different functions and the work of almost all diode is completely different from each other. Some diodes give light on supply and some diodes have completely different functions, so there are different types of diode, which are given below and the symbols are also given.

1. Zener Diode
2. Light Emitting Diode
3. Constant Current Diode
4. Schottky Diode
5. Shockley Diode
6. Photo Diode
7. Tunnel Diode
8. Varactor Diode
9. Laser Diode

Now discuss in detail about the diodes given above. I will also try to write the function and use of above diode.

1. Zener Diode

Zener diode is like a normal diode. But not everyone knows that what is the zener diode.I tell you that zener diode allows the current to go to one side like an ordinary diode, but when the voltage exceeds up to the breakdown voltage, it also allows the current to go in the reverse direction.

The Zener Diode was invented in 1934 by Clarence Zener. And this was done to avoid immediate voltage pulses. And this diode works like a voltage regulator.
Zener diode use and function
Zener Diode


2. Light Emitting Diode- LED

This diode converting electrical energy into light energy and this diode was invented in 1968. When it is properly coupled to the voltage supply, the electroluminescence action causes the holes and electrons to be reconnected to form the light. This diode works on the forward bias position.

Earlier this diode was used in Inductor lamp but now it is being used on a large scale and it is used for traffic signal camera flash etc. In an ordinary diode the radiated energy in the form of heat. In the Light Emitting Diode-LED, the radiated energy is in the form of light or photons.

By using materials such as gallium arsenide phosphide ( GaAsP)  and gallium phosphide (GaP), a manufacturer can produce LEDs that radiate red,green or orange lights.LED also used in instrument displays,panel indicators,digital watch,calculators,multimeters, intercoms, telephone switch boards.

Light Emitting Diode-LED work on low voltages 1 or 2V and current 5-10mA, and thus consume less power. LED require no heating,no warm-up time, and hence are very fastin action.
Light Emitting Diode use and function
LED


3. Constant Current Diode

This diode is also known as Current Regulating Diode, Constant Current Diode or Current Limited Diode or Diode Connector Transistor. The main function of this diode is to keep the voltage constant at particular current.

How does this diode two terminal current limiter work? And the JFET used to act as a current limiter to achieve high output impedance.

4. Schottky Diode

The large storage problem of a p-n junction can be minimized in a Schottky diode. It is accomplished by the setting up a barrier potential with a contact between a metal and a semiconductor.

This diode is made by semiconductor material and metal junction. And this diode is named after the German physicist Walter H. Schottky. It has a low voltage drop and acts very fast switching.

Due to the metal being in this diode, it has the ability to shed a large amount of current due to which the switching time in this is very short and it can do very fast switching. Because of the semiconductor and metal junction, The voltage blockage  in the diode is very low and the performance of the diode increases, so this diode is used in a high-frequency rectifier device.

Schottky diode maximum allowable voltage is limited to 100V. The current rating of Schottky diode varies from 1 to 300A. The Schottky diode are ideal for high-current and low voltage dc power supplies. However they are used in low-current power supplies for increased efficiency.
Schottky Diode function and symbol details
Schottky Diode symbol


5. Shockley Diode

Shockley diode was a semiconductor diode with a first four layer semiconductor diode. This was the first pnpn ”diode diode. Which was invented by William Shockley in the 1950s and also named after William Shockley.

Shockley diode used for the trigger switch for silicon controlled rectifier and relaxation oscillator / sawtooth oscillator. Shockley diode also used for the audio amplifiers.
Shockley Diode function and working details
Image of  Shockley Diode


6. Photo Diode

Photo diode is a semiconductor device that converts light into electrical current. This diode generates current when the photo is absorbed in the diode. The response time of photo diode is very short. And they are mostly used for solar power.

This diode works exactly the opposite of the light emitting diode. And the symbol below it is also a little different from the light emitting diode. Only the arrow marks in it are coming in. In the emitting diode, this mark is on the outside.
photo diode function and symbol
Photo diode

7. Tunnel Diode

This diode is used to switch very fast, where this diode is used where the work is to be done in nano seconds. This diode is invented by Leo Esaki in August 1957, hence it is also called Esaki diode.

Tunnel diode widely used in Oscillatory circuits, Microwave circuits and Resistant to nuclear radiation.
Tunnel Diode function and use detail explanation
Tunnel Diode


8. Varactor Diode

A reversed-biased PN-junction can be compared to a charged capacitor. The P and N regions are essentially low resistance areas due to high concentration of majority carriers. Varactor diode are replacing mechanically tuned capacitor in many applications.

A Varactor diode in parallel with an inductor gives a resonant tank circuit.The resonant frequency of this tank circuit can easily be changed by varying the reverse voltage across the diode.

This diode acts as a variable capacitor. And this diode works in reverse bias state. This diode can also change the capacitance of that circuit to a much higher value due to the constant voltage in a circuit. For this reason, this diode is used in many devices and this diode is used as a voltage control oscillator in cell phones, satellite pre-filters.

Varactor diode widely used in Voltage-controlled capacitors,Voltage-controlled oscillators,Parametric amplifiers and Frequency multipliers. Varactor diode also used in radio for FM transmitters and Phase locked loops, in television sets and cellular telephones.
Function and working details of Varactor diode
Function of Varactor Diode

9. Laser Diode

Laser diode is also known as LD and injection laser diode. It works like a light emitting diode but it creates a laser beam instead of the light. And today, laser diodes are used for fiber optic communication, barcode readers, laser pointers, CD / DVD / Blue-ray disc reading / recording, laser printing, laser scanning and light-beam illumination.

There are also many types of laser diodes which are used as per the need. Below I would like to mention the name of laser diode only.

Double Heterostructure Laser: Quantum Well Lasers: Quantum Cascade Lasers: .Separate Confinement Heterostructure Lasers: Distributed Bragg Reflector Lasers.
Use of Laser diode and function
Laser Diode


Last Word

In this post your friend Technosepidite has tried to give you complete information about how Diode works and its type. If you have any questions or suggestions besides this, comment below and ask. Technopediasite always waiting for your suggestion.