This document provides an overview of semiconductors and light emitting diodes (LEDs). It discusses the concept of energy bands in semiconductors and defines intrinsic and extrinsic semiconductors. N-type and P-type semiconductors are introduced along with the PN junction diode. The document then describes how LEDs work as PN junction diodes that emit light when forward biased. It discusses the contributions of scientists to developing LEDs and their advantages over incandescent lamps, such as energy efficiency and long lifetime. Some disadvantages of LEDs include higher initial costs and potential color shifts over time.
this is presentation about light emitting diode. it includes it working, figure and application. also shows the live example of led. it also contains its preference website..
any changes suggested are welcomed..
An LED is a device that emits light when electrically biased. Similar to any electronic component, LEDs also have electrical parameters that need to be taken into consideration when designed into a system.
Pn junction diode by sarmad baloch
I AM SARMAD KHOSA
BSIT (5TH A)
(ISP)
FACEBOOK PAGLE::
https://www.facebook.com/LAUGHINGHLAUGHTER/
YOUTUBE CHANNEL:::
https://www.youtube.com/channel/UCUjaIeS-DHI9xv-ZnBpx2hQ
this is presentation about light emitting diode. it includes it working, figure and application. also shows the live example of led. it also contains its preference website..
any changes suggested are welcomed..
An LED is a device that emits light when electrically biased. Similar to any electronic component, LEDs also have electrical parameters that need to be taken into consideration when designed into a system.
Pn junction diode by sarmad baloch
I AM SARMAD KHOSA
BSIT (5TH A)
(ISP)
FACEBOOK PAGLE::
https://www.facebook.com/LAUGHINGHLAUGHTER/
YOUTUBE CHANNEL:::
https://www.youtube.com/channel/UCUjaIeS-DHI9xv-ZnBpx2hQ
Polymer in the real life - Devoxx France - 2016 04-20Horacio Gonzalez
In the last two years I've been speaking a lot about web components and Polymer in conferences and user-groups, sharing a vision of the upcoming web-component revolution. But after these introductory talks I often got the same question: "that seems great... but does it works in Real Life?" Ah, the pesky real life question...
In this talk I'm going to tackle that question in the best way I know: I'm going to tell you my experience of almost two full years web applications with Polymer in the real life, for real projects in a real enterprise with real costumers, and all the lessons I've learnt from it.
You will heard why did I choose Polymer, how I dealt with the 0.x versions lifecycle, the good points and the bad ones too, how I did integrate lots of 3rd part libs into a component architecture and how now I'm able to create full fledge Progressive Web Apps using Polymer in a simple way without having to deal with the complexity of Angular/React/Whatever JS, but also how to integrate your components into those frameworks if needed.
Introduction
Semiconductor is a solid substance that has conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects. Devices made of semiconductors, notably silicon, are essential components of most electronic circuits.
Examples: Silicon, Germanium, Carbon
Intrinsic & Extrinsic Semiconductor
Semiconductors are mainly classified into two categories: Intrinsic and Extrinsic. An intrinsic semiconductor material is chemically very pure and possesses poor conductivity. It has equal numbers of negative carriers (electrons) and positive carriers (holes). Where as an extrinsic semiconductor is an improved intrinsic semiconductor with a small amount of impurities added.
The Doping of Semiconductors
The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors.
Pentavalent impurities
Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons.
Trivalent impurities
Impurity atoms with 3 valence electrons produce p-type semiconductors by producing a "hole" or electron deficiency.
N-Type Semiconductor
The addition of pentavalent impurities such as antimony, arsenic or phosphorous contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor. Phosphorous may be added by diffusion of phosphine gas (PH3).
P-Type Semiconductor
The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor creates deficiencies of valence electrons,called "holes". It is typical to use B2H6 diborane gas to diffuse boron into the silicon material.
Diodes
A device that blocks current in one direction while letting current flow in another direction is called a diode. Diodes can be used in a number of ways. For example, a device that uses batteries often contains a diode that protects the device if you insert the batteries backward. The diode simply blocks any current from leaving the battery if it is reversed -- this protects the sensitive electronics in the device.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
We all have good and bad thoughts from time to time and situation to situation. We are bombarded daily with spiraling thoughts(both negative and positive) creating all-consuming feel , making us difficult to manage with associated suffering. Good thoughts are like our Mob Signal (Positive thought) amidst noise(negative thought) in the atmosphere. Negative thoughts like noise outweigh positive thoughts. These thoughts often create unwanted confusion, trouble, stress and frustration in our mind as well as chaos in our physical world. Negative thoughts are also known as “distorted thinking”.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
2. Index
Semiconductors
Concept of Energy bands
intrinsic and extrinsic semiconductors
Concept of electrons and holes
N Type Semiconductors
P type semiconductors
P – N JUNCTION DIODE
P-n junction in forward bias and reverse bias
Graph for p-n junction at forward and reverse bias
LIGHT EMITTING DIODE ( led)
Major contributions of various scientists on LEDS
Research on Use of LED in place of incandescent lamps!!!
Basic Advantages of led light
Disadvantages of leds
3. Semiconductors
A semiconductor is a material which has electrical conductivity to a degree between that of a conductors
(such as copper) and that of an insulator (such as glass).
They have resistivity or conductivity intermediate to metals and insulators.
ρ ~ 10-5 – 106Ohm m
~ 105 – 10 -6 Sm-1
Semiconductors are the foundation of modern electronics, including transistors, solar cells, light-emitting
diodes (LEDs), quantum dots and digital and analog integrated circuits.
Concept of Energy bands
The group of discrete but closely spaced energy levels for the orbital electrons in the atoms is called
energy band.
o The upper empty energy band is called conduction band and the lower completely filled energy band is
called valence band. In between there is a group of energy levels which cannot be occupied by the
electrons and hence called the forbidden band. Electrons can jump to the conduction band from the
valence band without stopping in the forbidden band.
o The difference of energy between the conduction band and the valence band is forbidden energy gap (Eg).
4. For Silicon Eg = 1.1eV and for Germanium Eg = 0.7eV
Fermi Energy level
It is the maximum energy that an electron in the valence band
possesses at absolute zero is called Fermi energy and the level
corresponding to it is called Fermi Energy level.
Intrinsic semiconductor.
intrinsic and extrinsic semiconductors
A pure semiconductor is called
To increase the electrical conductivity the semiconductor is mixed with either pentavalent impurity (
Group 15) or trivalent impurity ( Group 13). The process is called doping. The doped semiconductor is
called Extrinsic semiconductor.
Generally one impurity atom is added for about 108 atoms of the semiconductor.
Concept of electrons and holes
When temperature rises, an electrons jumps from the valence band and jumps to the conduction
band a vacancy is created in the valence band. This vacancy is called hole. For an intrinsic
semiconductor the sample is electrically neutral and the number of free electrons is equal to the
number of holes in the valence band.
5. N Type Semiconductors
If a semiconductor is doped with a pentavalent
impurity ( Group 15 elements) such as
Arsenic(As),Antimony(Sb) , the extrinsic
semiconductor is called N Type semiconductors.
P type semiconductors
If a semiconductor is doped with a trivalent
impurity ( Group 13 elements) such as Aluminium
(Al) , Indium (In) , the extrinsic semiconductor is
called P Type semiconductor.
6. P – N JUNCTION DIODE
When a p –type semiconductor is suitably joined to an n – type semiconductor, their contact surface is
called p-n junction.
The electronic device consisting of a p-n junction is called diode.
Potential barrier: When a p-n junction is formed, the electrons diffuse across the junction from n-type to p-
type crystal du to concentration difference( of electrons.) Similarly holes diffuse from p-type to n-type
crystal. As a result the n-type crystal acquires a positive potential and p-type crystal acquires a negative
potential. The potential difference created across the p-n junction due to the diffusion of holes and
electrons is called barrier potential.
The potential difference blocks the diffusion of holes and a depletion layer is developed at the junction.
The thickness of depletion layer is about 10-6m.
7. P-n junction in forward bias and reverse bias
Forward Bias
Some concepts
Effective barrier height becomes VO - V.
Depletion layer decreases.
i. This is the principle on which LED works.
Reverse bias
Some Concepts
Effective barrier height becomes V + VO .
Depletion layer increases.
Where VO is the barrier potential.
9. LIGHT EMITTING DIODE ( led)
These are specially designed diodes which give out light radiations when forward biased.
It is heavily doped p-n junction.
On recombination, energy released in the form of photons.
Photons with energy equal to or slightly less than the band gap are emitted.
When the forward current of the diode is small, the intensity of light emitted is small.
As the forward current increases the intensity of light increases and reaches a maximum.
Further increases in the forward current results in decrease of light intensity.
The reverse breakdown voltages of LED are very low, typically around 5V.
LEDs that can emit red, yellow, orange, green and blue light.
LEDs are made of GaAs1-xPx ( Eg ~ 1.9eV for red LED) , GaAs(Eg~1.4eV) is used for making infrared LED
10. Major contributions by Various Scientists on LEDS
1920 -Oleg V. Losev studied the phenomena of light emitting diodes in radio sets. His first work on 'LEDs' involved a
report on light emission from SiC. In 1927 he published a detailed report but his work was not well known until the
1950s when his papers resurfaced.
1961 - Bob Biard and Gary Pittman developed the Infrared LED at Texas instruments. This was the first modern LED.
It was discovered by 'accident' while TI tried to make a laser diode. The discovery was made during a test of a tunnel
diode using a zinc diffused area of a GaAs (Gallium Arsenide) semi-insulating substrate.
1962 - Nick Holonyack Jr. develops the red LED, the first LED of visible light. He used GaAsP (Gallium Arsenide
Phosphide) on a GaAs substrate. General Electric.
11. Research on Use of LED in place of incandescent lamps!!!
Advantages of LEDs over conventional incandescent lamp are :
Low operational voltage and less power.
Fast action and no warm- up time required.
The bandwidth of emitted light is 100 A to 500 A or in other words it is nearly but
exactly monochromatic.
Long life and ruggedness
Fast on-off switching capability
12. Basic advantages of LED Light
Energy efficient - LED’s are now capable of outputting 135 lumens/watt
Long Lifetime - 50,000 hours or more if properly engineered
Rugged - LED’s are also called “Solid State Lighting (SSL) as they are made of solid material with no filament
or tube or bulb to break
No warm-up period - LED’s light instantly – in nanoseconds
Not affected by cold temperatures - LED’s “like” low temperatures and will start-up even in sub-zero weather
Directional - With LED’s you can direct the light where you want it, thus no light is wasted
Excellent Colour Rendering - LED’s do not wash out colours like other light sources such as fluorescents,
making them perfect for displays and retail applications
Environmentally friendly - LED’s contain no mercury or other hazardous substances
Controllable - LED’s can be controlled for brightness and colour.
OLED organic leds
These are LEDs in which the electroluminescent layer is made up of a film of organic compounds.Eg- poly(p-phenylene vinylene).
13. Disadvantages of leds
There are concerns that LEDs do not provide the warmth that ordinary bulbs give when lit.
LEDs are currently more expensive, on an initial capital cost basis, than more conventional lighting technologies.
However, when considering the total cost of ownership (including energy and maintenance costs), LEDs far surpass
incandescent or halogen sources and begin to threaten compact fluorescent lamps.
The Chart Below compares different light sources based upon the life of the bulb and the electrical cost at 10 cents per
kWh (kilowatt hour). Note: fixture costs and installation costs are not included.
LED performance largely depends on correctly engineering the fixture to manage the heat generated by the LED,
which causes deterioration of the LED chip itself. Over-driving the LED or not engineering the product to manage
heat in high ambient temperatures may result in overheating of the LED package, eventually leading to device
failure. Adequate heat-sinking is required to maintain long life. The most common design of a heat sink is a metal
device with many fins, which conducts the heat away from the LED.
LEDs must be supplied with the correct voltage and current at a constant flow. This requires some electronics
expertise to design the electronic drivers.
LED’s can shift colour due to age and temperature. Also two different white LED will have two different color
characteristics, which affect how the light is perceived.
14. Thank You
Special Thanks to the Foundation Course : Science and Life
As I could avail this great opportunity of making this presentation
“Since every opportunity is like a heartbeat so we should not miss it.”