What is Diode? An Introductory Guide
Published: 2021-09-13 08:21:28

The diode is a crucial device in electrical engineering. Diodes come in a range of forms and sizes and it could be utilized for a range of applications. Diodes are typically discovered in rectifiers, which are used to transform AC to DC transmitters. Among the applications are energy conversion, radio modulation, logic gates, temperature monitoring, and current management. This article will go over the complete basics on everything you need to know about diodes.

##Definition of a Diode
![Alt Text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8jtdkz9bgub3p66ar6yx.png)

A diode is a device that permits a unidirectional movement of electricity and possesses the greatest opposition to electricity travelling in the other path. It features two ends: an anode and a cathode. The positive end is the anode, and the negative end is the cathode. As a result, electricity could travel from the positive end to the negative end.

##Symbol of a Diode
![Alt Text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/eopq9yyvnqm8oylzob54.png)

The pointer depicts the route of the typical travelling of electricity in a situation where it is forward biased. The anode is attached to the p side, whereas the cathode is attached to the n side.

By doping pentavalent or donor impurities in an area of a silicon or germanium crystal block and trivalent or acceptor impurities in another, we might build a basic PN junction diode.

In the block's center, these dopings form a PN junction. A PN junction can also be created using a unique fabrication method to link a p-type and an n-type semiconductor combined. The anode is the part that gets attached to the p-type. The cathode is the end that connects the n-type side.

##Diode Working

During situations whereby two semiconductor components are combined, a temporary transfer of electric charge happens, leading to a depletion layer formation. Since no electricity is delivered to any terminals, you can refer to it as Zero Biasing State.

It features 2 additional biasing phases in functional situations:
* Forward biased
* Reverse biased

### Diode as Forward Biased

Although the PN Junction created at the intersection of 2 areas is modest, it is sufficiently potent that it can prevent free electrons from going through. So, if you are capable of applying some outside force to these electrons, they would be capable of breaking through this boundary and entering the P-Type zone. 

### Diode as Reverse Biased

During situations where the applied power's polarity is reversed, whenever the battery's positive end is linked to the cathode(-), and the negative end is attached to the anode(+), the depletion region expands. The diode is regarded to be reverse biased when it boycotts electricity from passing through it. It functions as though it were an open switch.

## Characteristics of a Diode

For clearer understanding, both the static and dynamic characteristics of a diode will be discussed here. On looking at the diagrammatic illustration below, you wouldn't need an elaborate interpretation. Although, here are some keywords needed for the description of a diode's characteristics.

The main static characteristics of a diode are:
* Forward voltage VF 
* Forward current IF
* Reverse voltage VR 
* Reverse current IR
![Alt Text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/6ychdsvjgv1wtx9if46f.png)

The useful region of rectification diodes is indicated by orange broken lines in the schematic illustration. It is the region inside the permissible IF level, and also the breakdown voltage span in the opposite path.

The part covered by the green broken lines is the usable part for zener diodes. Other diodes cannot be utilized in this region, and if it is penetrated with no IR limitations, gadget malfunction could ensue.

The two best dynamic characteristics are: 
* The reverse recovery time trr 
* The static capacitance Ct
![Alt Text](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/845wlesbe14qzgthltwc.png)

trr is the time needed for a voltage to be enforced in the forward path, and IF to travel before there would be alteration in the path of the voltage and the IR would go back to its steady state, usually zero.

The capacitance Ct is the diode's own capacitance, and it functions similarly to a capacitor.

##Types of Diode

There are several types of diodes, some of which are:
* [Zener Diode](https://www.theengineeringprojects.com/2019/09/what-is-the-zener-diode.html)
It is a part that operates on the Zener Breakdown principle. It was invented by Clarence Zener in 1934 and worked similarly to a regular diode in forward bias, letting electricity to pass. However, it only transmits in reverse bias in situations wherein the enforced current hits Zener Breakdown value. 

* Light Emitting Diode (LED)

Electrical energy is transformed into light energy by these diodes. In 1968, the initial batch was manufactured. The forward bias situation goes through an electroluminescence phase.

* Schottky Diode

The junction is achieved by connecting the semiconductor part with metal. The forward voltage loss experiences a reduction to the absolute minimum as a result of this. N-type silicon performs like it is the positive terminal, while metals like chromium, platinum, and tungsten serve as the negative.

* [Shockley Diode](https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/shockley-diode/)

It was among the first semiconductor gadgets created. The Shockley diode comprises four layers. It is also regarded as a PNPN diode. It is similar to a thyristor without the need for a gate terminal, which implies it is not hooked. Because there is no trigger input, it is only capable of conductivity by supplying forward current.

* Tunnel Diode

It is utilized as an elevated controller, featuring switching times in the nanosecond range. It operates relatively quickly in the microwave frequency range owing to the tunneling impact. It features an extreme number of dopants.

* Varactor Diode

Varicap diodes are another name for these. It functions similarly to a variable capacitor. The majority of actions are carried out in the reverse bias state. It is popular for its capacity to change the capacitance varies inside a circuit while maintaining a steady current circulation.

* Peltier Diode

Heat is accomplished by a semiconductor's P-N junction, and it travels via one end to the reverse. This circulation only has one path, that is identical to the present electricity path.

##Applications of a Diode

* A waveform clipper is a tool utilized for the reduction of a waveform's size.
* Included for extraction of the amplitude signal.
* It is utilized for the regulation of electricity passage.
* Rectifiers are constructed by utilizing this device for the conversion of AC signals to DC signals.

##Conclusion

All diodes feature their advantages and uses. Some are popularly utilized in numerous manners all over several domains, while some are only utilized for limited applications.