Difference between led & lcd

Whats difference between an LCD & LED,its confusing many time,therefore for better understanding,i make it.

1. LED & LCD ELECTRONICS AND COMMUNICATION ENGINEERING POORNIMA INSTITUTE OF ENGINEERING & TECNOLOGY, JAIPUR A PRESENTATION ON SUPERVISED BY: Mr. Rahul Gupta Assistant Professor SUBMITTED BY: Madhusudhan Agarwal

2. What is LED? Semiconductors bring quality to light! A light emitting diode (LED) is essentially a PN junction opto- semiconductor device. It emits a monochromatic (single color) light when operated in a forward biased direction. LEDs convert electrical energy into light energy.

3. How Does A n Work ? 3 When sufficient voltage is applied to the chip across the leads of the LED, electrons can move easily in only one direction across the junction between the p and n regions . When a voltage is applied and the current starts to flow, electrons in the n region have sufficient energy to move across the junction into the p region .

4. How Does A LED Work ? 4 1.Each time an electron recombines with a positive charge, electric potential energy is converted into electromagnetic energy . 2.For each recombination of a negative and a positive charge, a quantum of electromagnetic energy is emitted in the form of a photon of light with a frequency characteristic of the semi-conductor material (usually a combination of the chemical elements gallium, arsenic and phosphorus)..

5. Inside a Light Emitting Diode Transparent Plastic Case Terminal Pins Diode                                                                                                                                                                                                                                         

6. Driving LEDs Two type of DRIVING LED Analog LED Drive Circuits Digital LED Drive Circuits 6                               

7. Analog LED Drive Circuit 7

8. Digital LED Drive Circuits 8

9. Bargraph 7-segment Starburst Dot matrix 9 Some Types of LEDs

10. Advantage of an LED Efficiency is high Small size On/Off time is less . Slow failure Lifetime

11. Applications of an 11 Sensor Applications Mobile Applications Sign Applications Automative Uses LED Signals Indicators

12. Liquid-Crystal (LCD ) Displays

13. 1.   What’s Liquid Crystals (LC) intermediary substance between a liquid and solid state of matter. e.g. soapy water light passes through liquid crystal changes when it is stimulated by an electrical charge. 13

14. 2.   Introduction to Liquid Crystal Displays A liquid-crystal display ( LCD ) is a flat panel display that uses the light modulating properties of liquid crystals . Liquid crystals do not emit light directly It consists of an array of tiny segments (called pixels) that can be manipulated to present information Using polarization of lights to display objects Common wrist watch and pocket calculator to an advanced VGA(video graphic array) computer screen 14

15. Different types of LCDs There are Two type of LCDs available 1.Passive Matrix LCDs 2.Active Matrix LCDs 15

16. Active Matrix V/S Passive Matrix LCDs Active Matrix LCD Allow very high resolution It isn`t limited to about 50 rows Each sub-pixel is individually controlled by an isolated thin-film transistor (TFT). More use in Laptop & TV Passive Matrix LCD Allow high resolution It is usually limited to about 50 rows Each sub-pixel is not individually controlled by an isolated thin-film transistor (TFT). Less use in Laptop & TV

17. LCD Display Technology Technology Enhancements: Better color through corrected CCFLs, LEDs Improved black levels (compensating films) Higher contrast (pulsed backlights) Wider viewing angles (compensating films) Higher resolution ( 1920x1080) Improved LC twist times

18. Advantages Very compact and light. Low power consumption. Very little heat emitted during operation, due to low power consumption. No geometric distortion . Is very thin compared to a CRT monitor, which allows the monitor to be placed farther back from the user, reducing close-focusing related eye-strain. Can be made in almost any size or shape. No theoretical resolution limit. Can be made to large sizes (more than 24 inches) lightly and relatively inexpensively. .

19. Applications Thin Film Transistor (TFT) Alpha-numeric display Back lighting systems For brighter displays

20. Comparison Between LED & LCD LED Power Consumption is less F aster response rate time Sizes Available 17inches and 70inches .   Color Accuracy is less Cannot be extremely slim LCD Power Consumption is more Slower response rate time Sizes Available 15inches to 65 inches Color Accuracy is more Can be extremely slim

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