History of Diode

In the year 1940 at Bell Labs, Russell Ohl was operating with a chemical element crystal to seek out out its properties. in the future accidentally once the chemical element crystal that encompasses a crack in it had been exposed to the daylight, he found the flow of current through the crystal which was later referred to as-as a diode, that was the start of the semiconductor era. the invention of uneven conductivity across the contact between a crystalline mineral and a metal was created by German scientist Ferdinand Braun in 1874. Today, most diodes are made from a chemical element, however alternative materials like metallic element compound and element are used.


A diode may be a two-terminal electronic part that conducts current primarily in one direction its low resistance in one direction, and high resistance within the alternative. within the previous tutorial, we have a tendency to saw the way to build a semiconductor unit material by doping a chemical element atom with tiny amounts of metal and conjointly the way to build a semiconductor material by doping another chemical element atom.


     Fig: Diode Symbol

The result’s that a number of the free electrons from the donor impurity atoms begin to migrate across this new shaped junction to refill the holes within the P-type material manufacturing negative ions. The contact diode may be a 2 terminal device. this is often the essential construction of the contact diode.

it’s one in every of the best semiconductor devices because it permits current to flow in just one direction. The diode doesn’t behave linearly with relevance the applied voltage, AND it’s an exponential V-I relationship.

P-Type Semiconductor 

In the semiconductor, the population of holes within the valence band is additional, whereas the population of free electrons within the physical phenomenon band is a smaller amount. So, a current physical phenomenon is principally attributable to holes within the valence band.

P-Type Semiconductor

            Fig: P-Type Semiconductor

Free electrons in physical phenomenon band represent a bit currently. therefore within the semiconductor, holes square measure referred to as majority carriers and free electrons square measure referred to as minority carriers. because the range of holes is excess in fresh shaped material these square measure referred to as-as P-type semiconductors. In P-type semi-conductor holes square measure majority charge carriers and electrons square measure minority charge carriers.

N-Type Semiconductor

In Associate in Nursing semiconductor device, the population of free electrons is a lot of whereas the population of holes is a smaller amount. thus in a semiconductor device, free electrons area unit referred to as majority carriers and holes area unit referred to as minority carriers. Therefore, in an exceeding semiconductor device conductivity is principally owing to the motion of free electrons.

N-Type Semiconductor

      Fig: N-Type Semiconductor

As the electrons area unit, a lot of in variety these area unit referred to as-as Associate in Nursing semiconductor device. In N-type, semi-conductor electrons area unit majority charge carriers and holes area unit minority charge carriers.

P-N junction :

A P-N junction diode is formed of a crystal of a semiconductor, typically element, however, element and metallic element chemical compound are used. The word diode is often explained as ‘Di’ suggests that 2 and ‘ode’ is obtained from the conductor. because the fresh shaped element will have 2 terminals or electrodes (one connected to P-type and also the difference to the N-type) it’s referred to as-as a diode or tangency diode or semiconductor.

P-N junction semiconductor

      Fig: P-N junction semiconductor

This is all well and smart, however, these fresh doped N-type and semiconductor device materials do little on their own as they’re electrically neutral. However, if we tend to be a part of (or fuse) these 2 semiconductor materials along they behave in a very completely different approach merging along and manufacturing what’s typically called a “P-N Junction“.

The diode’s terminals square measure hooked up to the n-type and p-type regions. The boundary between these 2 regions referred to as a P–N junction is wherever the action of the diode takes place. A semiconductor facilitates the flow of electrons fully in one direction solely – that is that the main operation of a semiconductor. It also can be used as a Rectifier.

The distance of PN Junction :

As the N-type material has lost electrons and also the P-type has lost holes, the N-type material has become positive with relevancy the P-type. Then the presence of impurity ions on either side of the junction causes an electrical field to be established across this region with the N-side at a positive voltage relative to the P-side.

A suitable positive voltage applied between the 2 ends of the P-N junction will offer the free electrons and holes with the additional energy. The external voltage needed to beat this potential barrier that currently exists is extremely abundant dependent upon the kind of semiconductor material used and its actual temperature.

Reverse Bias :

If an associate degree external voltage is placed across the diode with identical polarity because of the intrinsic potential, the depletion zone continues to act as associate degree stuff, preventing any vital current flow.

If negative terminal of a voltage supply is applied to the anode or P-Region of the diode and positive terminal to the cathode or N-Region of the diode, it’s same to be Reverse biased. however, if we tend to persist increase the voltage, at some extent barrier or depletion region cannot withhold the external force and therefore the junction breaks down which can generally cause the traditional diode injury for good. to beat this we will heavily dope the regions and place the diode safe, this application will be seen in Zener diodes.

Forward Bias :

However, if the polarity of the external voltage opposes the inbuilt potential, recombination will another time proceed, leading to a considerable electrical phenomenon through the P–N junction. This affiliation is additionally known as giving a positive voltage. Electrons from the N-region cross the junction and enters the P-Region. because of the attraction that’s generated within the P-region the electrons area unit attracted and move towards the positive terminal. at the same time, the holes area unit attracted toward the negative terminal of the battery.

If a positive terminal of the battery or a voltage supply is applied to the anode or P-Region of the diode and negative terminal to the cathode or N region of the diode, it’s aforesaid to be forward biased. The diode is often aforesaid to possess a forward “threshold” voltage, on top of that it conducts and below that physical phenomenon stops. However, this is often solely associate degree approximation because the forward characteristic is swish.

I-V Characteristic Curve of a Diode :

The current-voltage, (I-V) Characteristics Curves outline the operation characteristics of an associated device. as an example, the “current-voltage characteristics” of a bipolar junction transistor is shown with varying amounts of base drive or the I-V characteristic curves of a diode in operation in each its forward and reverse regions. When the forward voltage exceeds the diodes P-N-junctions internal barrier voltage, that for Si is concerning zero.7 volts, associate avalanche happens and therefore the forward current will increase quickly for a really tiny increase in voltage manufacturing a non-linear curve. The “knee” purpose on the forward curve.

semicondutor I-V Characteristic

  Fig: semiconductor I-V Characteristic

The characterisic function of a junction diode is additionally known as associate degree I-V Curve. it’s usually a graph showing this flow at totally different forward voltages. The current-voltage characteristics of associate degree electronic part tell United States of America abundant concerning its operation and might be a really useful gizmo in deciding the operative characteristics of a specific device or part by showing its potential combos of current and voltage, and as a graphical aid will facilitate visually perceive higher what’s happening inside a circuit.
The current is usually on the coordinate axis and also the voltage on the coordinate axis. this kind of graph provides engineers with a visible record of the operative characteristics of the part. This data allows them to use the part additional befittingly inside a circuit. There are many alternative sorts of diodes, and that they all have totally different characteristic curves and applications. Here are some diodes you may bump into within the future: Zener, Germanium, Gunn, Tunnel, and Schottky. this text appearance at a typical semiconductor diode. this can be all concerning contact diode’s theory, regulation, and its applications. we tend to believe that the data given during this article is useful to you for a far better understanding of this idea. moreover, for any queries concerning this text or any facility in implementing electrical and natural philosophy comes, you’ll be able to approach the United States of America by commenting within the comment section below.