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DIODES Applications

DIODES Applications. EE314. Diodes applications. LED – Light Emitting Diodes LD – Laser Diodes Fiber optics Optical switching MEMS Nanotechnology Solar Cells Light Detection Future Technologies.

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DIODES Applications

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  1. DIODESApplications EE314

  2. Diodes applications • LED – Light Emitting Diodes • LD – Laser Diodes • Fiber optics • Optical switching MEMS • Nanotechnology • Solar Cells • Light Detection • Future Technologies Green electroluminescence from a point contact on a crystal of SiC recreates H. J. Round's original experiment from 1907.

  3. Light Spectrum

  4. Light Spectrum Red, green and blue LEDs

  5. LED - Light Emitting Diodes When a light-emitting diode is forward biased, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. Source http://en.wikipedia.org/wiki/Light-emitting_diode

  6. LED - Light Emitting Diodes UV – AlGaN Blue – GaN, InGaN Red, green – GaP Red, yellow – GaAsP IR- GaAs

  7. LED - Colors & voltage drop

  8. Wireless telemedicine The PillCam is a ‘swallow’ diagnostic device, taking high-quality, high-speed photos as it passes through the esophagus. PillCam transmits 14 pictures/sec. to a receiver worn by the patient. This enables diagnosis of throat disease and related ailments. http://www.three-fives.com/latest_features/feature_articles/250205medical.html

  9. pn-junction laser Light Amplification by Stimulated Emission of Radiation

  10. Diode Lasers are Small! http://faculty.uml.edu/carmiento/Special%20Lectures/Intro%20to%20EE%20Lecture.pdf

  11. Radar/Laser Detectors A radar/laser detector is a combination of a radar detector, which senses radar in the air, and a laser detector, which looks for laser beams directed at your car. A laser beam is a very focused beam of light that does not separate out from its beam path. Fortunately, there is a lot of dust and fine particles in the air, which causes the laser beam to separate enough that the beams can be seen by a proper detector.

  12. Optical Fiber Communications • What is it? • Transmission of information using light over an optical fiber • Why use it? • –Extremely high data rate and wide bandwidth • –Low attenuation (loss of signal strength) • –Longer distance without repeaters • –Immunity to electrical interference • –Small size and weight • –Longer life expectancy than copper or coaxial cable • –Bandwidth can be increased by adding wavelengths

  13. Information Capacities in Optical Fiber • •Each wavelength can carry a signal at 10 gigabits/sec (1010 bits/sec) • •A fiber can transport up to 64 different wavelengths • –Each wavelength can carry 10 Gb/s • –Unlike electrical signals, optical signals inside the same fiber at different wavelengths don’t interfere with each other • •Each fiber can have an aggregate data rate of 640 Gb/s • –This is 640,000,000,000 bits per second! • •This rate translates to: • –10 million simultaneous telephone calls (64 kb/s each) • –Download the contents of the Library of Congress takes: • •84 years using a 56 kb/s modem • •0.22 seconds using the aggregate fiber rate • •These rates can go much higher! • –Researchers have developed operation of 40 Gb/s per wavelength • –A fiber cable can contain as much as a hundred fibers

  14. Cable Size Comparison: Copper vs. Fiber This is a standard copper cable used for telephone service. This carries about 300 phone calls One of these fibers can carry up to 10 million telephone calls

  15. Optical Switching Where electrical and mechanical engineering meet Route optical communication signals without conversion to the electronic domain using microscopic mirrors based on MEMS technology

  16. Nanotechnology Small and getting smaller Video 2:30 min MEMS: Miniature Motors Human hair

  17. Micro and nanotechnologies are revolutionizing medicine Almost invisible' tools are being developed by European researchers to discover diseases earlier and to treat patients better. The miniaturization of instruments to micro and nano dimensions promises to make our future lives safer and cleaner. In the "Adonis"-project, nano-sized gold particles are used to detect prostate cancer cells at an early stage. Video 7:30 min http://www.zangani.com/node/2763

  18. Photovoltaics The word Photovoltaic is a combination of the Greek word for Light and the name of the physicist Allesandro Volta. It identifies the direct conversion of sunlight into energy by means of solar cells. The conversion process is based on the photoelectric effect discovered by Alexander Bequerel in 1839. The photoelectric effect describes the release of positive and negative charge carriers in a solid state when light strikes its surface. http://www.solarserver.de/wissen/photovoltaik-e.html

  19. Photovoltaics

  20. How Does a Solar Cell Work? Solar cells are composed of various semiconducting materials. Semiconductors become electrically conductive when supplied with light or heat. Over 95% of all the solar cells are composed of the Si.

  21. How Does a Solar Cell Work? Photo generated current The equivalent circuit of a solar cell The usable voltage from solar cells depends on the semiconductor material. In silicon it amounts to approximately 0.5 V. Terminal voltage is only weakly dependent on light radiation, while the current intensity increases with higher luminosity. A 100 cm² silicon cell, for example, reaches a maximum current intensity of approximately 2 A when radiated by 1000 W/m².

  22. Characteristics of a Solar Cell • The output power of a solar cell is temperature dependent. • Higher cell temperatures lead to lower output, and hence to lower efficiency. • Efficiency indicates how much of the radiated quantity of light is converted into useable electrical energy. • Today on the order of 15-25%

  23. Light Detectors Optical detectors, Chemical detectors, Photoresistors or Light Dependent Resistors (LDR) Photovoltaic cells or solar cells Photodiodes Phototransistors Optical detectors that are effectively thermometers, responding to the heat by the incoming radiation, such as pyroelectric detectors, Golay cells, thermocouples and thermistors, Cryogenic detectors are sufficiently sensitive to measure the energy of single x-ray Charge-coupled devices (CCD),

  24. CCD Detectors An image is projected by a lens on the capacitor array causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A charge-coupled device (CCD) is an analog shift register that transports electric charges through successive capacitors, controlled by a clock signal. CCDs are used in digital photography, digital photogrammetry, astronomy, sensors, electron microscopy, medical fluoroscopy, optical and UV spectroscopy,etc. CCD used for ultraviolet imaging in a wire bonded package. CCD color sensor

  25. CCD Detectors

  26. Testing an LED Never connect an LED directly to a battery or a power supply!It will be destroyed almost instantly because too much current will pass through and burn it out. LEDs must have a resistor in series to limit the current to a safe value, for quick testing purposes a 1kΩ resistor is suitable for most LEDs if your supply voltage is 12V or less. Remember to connect the LED the correct way!

  27. Tri-color LEDs The most popular type of tri-color LED has a red and a green LED combined in one package with three leads. They are called tri-color because mixed red and green light appears to be yellow. The diagram shows the organization of a tri-color LED. Note the different lengths of the three leads. The central lead (k) is the common cathode for both LEDs, the outer leads (a1 and a2) are the anodes to the LEDs allowing each one to be lit separately, or both together to give the third color.

  28. Calculating an LED resistor value An LED must have a resistor connected in series to limit the current through the LED. The resistor value, R is given by: VS = supply voltage VL = LED voltage (usually 2V, but 4V for blue and white LEDs) I = LED current (e.g. 20mA), this must be less than the maximum permitted If the calculated value is not available, choose the nearest standard resistor value which is greater, to limit the current. Even greater resistor value will increase the battery life but this will make the LED less bright. For example If the supply voltage VS = 9V, and you have a red LED (VL = 2V), requiring a current I = 20mA = 0.020A, R = (9V - 2V) / 0.02A = 350, so choose 390 (the nearest greater standard value).

  29. Connecting LEDs in series If you wish to have several LEDs on at the same time, connect them in series. This prolongs battery life by lighting several LEDs with the same current as just one LED. The power supply must have sufficient voltage to provide about 2V for each LED (4V for blue and white) plus at least another 2V for the resistor. To work out a value for the resistor you must add up all the LED voltages and use this for VL.

  30. Connecting LEDs in series Example A red, a yellow and a green LED in series need a supply voltage of at least 3×2V + 2V = 8V, so choose a 9V battery. Adjust the resistor R to have current I=15 mA.

  31. Connecting LEDs in series Example A red, a yellow and a green LED in series need a supply voltage of at least 3×2V + 2V = 8V, so choose a 9V battery. Adjust the resistor R to have current I=15 mA. VL = 2V + 2V + 2V = 6V (the three LED voltages added up). If the supply voltage VS is 9V and the current I must be 15mA = 0.015A, Resistor R = (VS - VL) / I = (9 - 6) / 0.015 = 3 / 0.015 = 200, so choose R = 220Ω   (the nearest standard value which is greater).

  32. Avoid connecting LEDs in parallel! Connecting several LEDs in parallel with just one resistor shared between them is a bad idea. If the LEDs require slightly different voltages only the lowest voltage LED will light and it may be destroyed by the larger current flowing through it. If LEDs are in parallel each one should have its own resistor.

  33. LED Displays It is a common anode display since all anodes are joined together and go to the positive supply. The cathodes are connected individually to resistors limiting the current through each diode to a safe value. LED displays are packages of many LEDs arranged in a pattern, the most familiar pattern being the 7-segment displays for showing numbers (digits 0-9).

  34. Using Varicap Diode When the junction diode is reverse biased, the insulating barrier widens reducing diode capacitance. The barrier forms the dielectric, of variable width, of a capacitor. The N and P type cathode and anode are the two plates of the capacitor. In the diagram, the diode and coil form a resonant circuit. The capacitance of the diode, and thereby the resonant frequency, is varied by means of the potentiometer controlling the reverse voltage across the varicap. The capacitor prevents the coil shorting out the voltage across the potentiometer.

  35. Diode Capacitance as a Funcion of VD • Ideality factor (m) depends on junction gradient

  36. Nanotechnology 101 Nanotechnology is the art and science of manipulating matter at the nanoscale (down to 1/100,000 the width of a human hair) to create new and unique materials and products. Nanotechnology has enormous potential to change society. • An estimated global research and development investment of nearly $9 billion per year is anticipated to lead to: • new medical treatments and tools; • more efficient energy production, storage and transmission; • better access to clean water; • more effective pollution reduction and prevention; • and stronger, lighter materials and many other uses.

  37. Nanotechnology 101 So what? The nanoscale is the scale of atoms and molecules. At the nanoscale, scientists can start affecting the properties of materials directly, making them harder or lighter or more durable. • In some cases, simply making things smaller changes their properties: • a chemical might take on a new color, or • start to conduct electricity. • nanoscale particles are more chemically reactive with more surface area • nanotubes made of carbon, can be up to thirty times stronger than steel, yet is one sixth the weight. http://www.nanotechproject.org/topics/nano101/introduction_to_nanotechnology/

  38. Nanotechnology 101 nanotubes Dollars and Sense In 2007, $60 billion worth of nano-enabled products were sold. Nanotechnology will produce an anticipated 7 million jobs in the next decade. By 2014, $2.6 trillion in manufactured goods will incorporate nanotechnology. • Carbon nanotubes make bicycle frames and tennis rackets lighter and stronger. • Nano-sized particles of titanium dioxide and zinc oxide are used in sunscreens. • Nanoscale silver is antimicrobial and prevents food stored in plastic bags from going bad. • Clothes treated with nano-engineered coatings are stain-proof or static-free. • Computer chips using nanoscale components are used anywhere from computers to mp3 players, digital cameras to video game consoles

  39. Future Technologies Future technology videos Part1: 7:00 min Part2: 7:50 min Part3: 7:22 min Part4: 8:24 min Part5: 7:30 min

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