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Post on 31-Jul-2015




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1. 1 2. In electronics, a diode is a two terminal electronic component withasymmetric conductance; it has low (ideally zero) resistance to current in onedirection, and high (ideally infinite) resistance in the other.2 3. P-N junction diode ZENER diode LIGHT EMITTING diode PHOTO diode3 4. P-N junctiondiodePHOTO diodeLIGHTEMITTINGdiodeZENER diode4 5. A pn junction diode is made of a crystal of semiconductor, usually silicon, but germaniumand gallium arsenide are also used. Impurities are added to it to create a region on one side that contains negativechargecarriers (electrons), called n-type semiconductor, and a region on the other side that contains positivecharge carriers (holes), called p-type semiconductor. When two materials i.e. n-type and p-type are attached together, a momentary flow of electronsoccur from n to p side resulting in a third region where no charge carriers are present.5 6. ZERO BIAS no potential is applied FORWARD BIAS- when p-type is connected with+terminal and n-type is connected with terminal of the source REVERSE BIAS-when p-type is connected withterminal and n-type is connected with+terminal of the source6 7. FORWARDBIASREVERSE BIAS7 8. HALF WAVE RECTIFIER FULL WAVE RECTIFIER1- CENTER TAP FULL WAVE RECTIFIER2-BRIDGE RECTIFIER8 9. A simple Half Wave Rectifier is nothing more than a single pnjunction diode connected in series to the load resistor. If you lookat the above diagram, we are giving an alternating current asinput. Input voltage is given to a step down transformer and theresulting reduced output of transformer is given to the diode Dand load resistor RL. The output voltage is measured across loadresistor RL.9 10. In this simplified (ideal diode) case the input and outputwaveforms are as shownThe diode must withstand a peak inversevoltage of V M10 11. The average d.c. value of this half-wave-rectified sine wave is1VAV VM d 0sin 02VM VM cos cos0 211 12. So far this rectifier is not very useful.Even though the output does not change polarityit has a lot of ripple, i.e. variations in outputvoltage about a steady value.12 13. A full-wave rectifier converts the whole of theinput waveform to one of constant polarity(positive or negative) at its output. Full-waverectification converts both polarities of theinput waveform to pulsating DC (directcurrent), and yields a higher average outputvoltage.13 14. The average and root-mean-square no-load outputvoltages of an ideal single-phase full-wave rectifier are:14w w 15. As shown in the given diagram of fullwave bridge rectifier it consists of fourdiodes under the condition in whichfour diodes are connected the calledbridge circuit. So due to this type ofcircuit is named bridge rectifier. Aresistor is connected in the circuitwhiere rectified output voltage appearscalled load resistor RL15 16. The four diodeslabelled D1 to D4 are arranged inseries pairs with only two diodesconducting current during each halfcycle. During the positive half cycleof the supply,diodes D1 and D2conduct in serieswhile diodes D3 and D4 are reversebiased and the current flows throughthe load as shown above.16 17. A Zener diode is a diode which allows current toflow in the forward direction in the same manner asan ideal diode, but also permits it to flow in thereverse direction when the voltage is above a certainvalue known as the breakdown voltage, "Zener kneevoltage", "Zener voltage", "avalanche point", or "peakinverse voltage".17 18. 18 19. A)Line RegulationIn this type of regulation, series resistance and load resistance areFixed, only input voltage is changing. Output voltage remains thesame as long as the input voltage is maintained above a minimumvalue.Percentage of line regulation can be calculated by =where V0 is the output voltage and VIN is the inputvoltage and V0 is the change in output voltage for a particularchange in input voltage VIN.19 20. b) Load RegulationIn this type of regulation, input voltage is fixed and the load resistanceis varying. Output volt remains same, as long as the load resistance ismaintained above a minimum value.20 21. A light-emitting diode (LED) is a two-lead semiconductor lightsource.It is a basic pn-junction diode, which emits light whenactivated.When a fitting voltage is applied to theleads, electrons are able to recombine with electron holes withinthe device, releasing energy in the form of photons.This effect is called electroluminescence, and the color of thelight (corresponding to the energy of the photon) is determined bythe energy band gap of the semiconductor.21 22. INDICATOR AND SIGNS LIGHTING Data communication and other signaling Light sources for machine vision systems Energy consumption22 23. DISPLAY BOARDS TRAFFIC LIGHTS DAY TIMERUNNING LIGHTSLED panel light source used in anexperiment on plant growth23 24. 24