Diode Applications Experiment 5

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Diode Applications Experiment 5

  1. 1. ELECTRICAL ENGINERING LABORATORY 1 EEE230 EXPERIMENT 5 DIODE APPLICATION 1
  2. 2. CONTENTS Title PageIntroduction/theory PART A:3-4 PART B:9-10 Result PART A:5-6 PART B:11-13Discussion/Question PART A:7-8 PART B:14 Conclusion 15 References 16 2
  3. 3. PART A ; Rectifier circuit using diodeIntroductionIn this experiment, we have learned about the applications of diode. First, we wererevising the basic of equipments handling. Secondly. we were knew that one of themain component used in the making of rectifier circuits are diodes and there arethree types of rectifier circuits Thirdly, we have been introduced to the function ofa capacitor in a rectifier circuit. Lastly, we also have learned about how to build asimple diode clipping and diode clamping circuitsTheory Usually we have three main type of rectifier it is a half-wave rectifier circuit,center tap full-wave rectifier circuit and full-wave bridge rectifier circuit. Firstly about half-wave rectifier circuit, when diode was connect to sourceAC voltage supply, itwill be alternatelyforward-biased, and then reverse-biased,during each cycle of the AC sine-wave. When a singlediode is used in a rectifiercircuit, current will flow through the circuit only during one-half of the inputvoltage cycle like in figure below. For this reason, this rectifier circuit is called ahalf-wave rectifier. The output of a half-wave rectifier circuit is pulsating DC. Second is about center tap full-wave rectifier circuit is uses two diodesconnected to the secondary of a center tapped transformer. The AC on each side of 3
  4. 4. the center-tap is ½ of the total secondary voltage. Only one diode will be biased onat a time the prose to be center tap full-wave rectifier is like below. Last is about full-wave bridge rectifier circuit, The Bridge is shown in thefigure below. The circuit has four diodes connected to form a bridge. The ac inputvoltage is applied to the diagonally opposite ends of the bridge. The loadresistance is connected between the other two ends of the bridge. 4
  5. 5. RESULT PART AExperiment 5.1Without capacitor With capacitorExperiment 5.2Without capacitor With capacitor 5
  6. 6. Experiment 5.3 Without capacitor with capacitor Input Output dc output voltage Ripple voltage (without capacitor) (with capacitor)Half-wave rectifier 6.60V 0.80VCenter tap full-wave rectifier 5.56V 0.38VFull-wave bridge rectifier 5.52V o.43V 6
  7. 7. DISCUSSIONBased on the experiment above, on the first positive half cycle the diode conducts charging thecapacitor left. This is on the right end, the right end of the capacitor with respect to the ground. Itis also has an AC peak sine wave coupled across it from source to node. The sum of the two isa peak sine riding on a negative DC level. The diode only conducts on successive positiveexcursions of source V if the peak exceeds the charge on the capacitor. This only happens if thecharge on the capacitor drained off due to a load. The charge on the capacitor is equal topositive peak of V. The AC riding on the negative end, right end, is shifted down. The positivepeak of the wave form is clamped to 0V because the diode conducts on the positive peak. In the negative cycle of the input AC signal, the diode is forward biased and conducts,charging the capacitor to the peak positive value. During the positive cycle, the diode is reversebiased and thus does not conduct. The output voltage is therefore equal to the voltage stored inthe capacitor plus the input voltage gain. In the positive cycle of the input AC signal, the diode is forward biased and conducts,charging the capacitor to the peak voltage value. During the negative cycle, the diode is reversebiased and thus does not conduct. The output voltage is therefore equal to the voltage stored inthe capacitor plus the input voltage gain, so Vout = negative. A positive biased voltage clamp is identical to an equivalent but with output voltageoffset by the bias amount. A negative biased voltage clamp but with the output voltage offset inthe negative direction by the bias amount. Based on the experiment above, on the first positive half cycle the diode conductscharging the capacitor left. This is on the right end, the right end of the capacitor with respect tothe ground. It is also has an AC peak sine wave coupled across it from source to node. The sumof the two is a peak sine riding on a negative DC level. The diode only conducts on successivepositive excursions of source V if the peak exceeds the charge on the capacitor. This onlyhappens if the charge on the capacitor drained off due to a load. The charge on the capacitor is 7
  8. 8. equal to positive peak of V. The AC riding on the negative end, right end, is shifted down. Thepositive peak of the wave form is clamped to 0V because the diode conducts on the positivepeak. In the negative cycle of the input AC signal, the diode is forward biased and conducts,charging the capacitor to the peak positive value. During the positive cycle, the diode is reversebiased and thus does not conduct. The output voltage is therefore equal to the voltage stored inthe capacitor plus the input voltage gain. In the positive cycle of the input AC signal, the diode is forward biased and conducts,charging the capacitor to the peak voltage value. During the negative cycle, the diode is reversebiased and thus does not conduct. The output voltage is therefore equal to the voltage stored inthe capacitor plus the input voltage gain, so Vout = negative. A positive biased voltage clamp is identical to an equivalent but with output voltageoffset by the bias amount. A negative biased voltage clamp but with the output voltage offset inthe negative direction by the bias amount. 8
  9. 9. PART B:Diode clipping and clamping circuit.TheoryDiode characteristics From the figure above we can see the diode has a terminal not like thetransistor. The negative (-ve) terminal is know as cathode and for positive (+ve)terminal is know as anode. Diode in electrical is a component just allow electricity flow in one direction fromanode to cathode. The diode can become conductor went the diode are place inforward bias and also become insulator if place in reverse bias.Like the figure (a) the diode become a conductor because went diode in forwardbias the resistance in diode become lower and in figure (b) the diode becamehigher resistance because of that the current cannot through it. 9
  10. 10. Diode clipping circuitA clipping circuit consists of linear elements like resistors and non-linear elementslike junction diodes or transistors, but it does not contain energy-storage elementslike capacitors. This clipping function is to cut the upper or the lower portion ofsignal this figure below is example the circuit for diode clipping circuit.Diode clamping circuitThe clamping circuit is difference with the clipping circuit, because the clampingcircuit are build is to clamp to a required DC level, basically the circuit ofclamping is the load was parallel with diode like in figure below. 10
  11. 11. RESULT PART BPART 1 Waveform Result for Figure 5.7 Waveform Result for Figure 5.8 11
  12. 12. Waveform Result for Figure 5.9Waveform Result for Figure 5.1 12
  13. 13. PART 2 13
  14. 14. DISCUSSIONPart 1 Clipping Circuit : Principles of operationThe schematic of a clamper reveals that it is a relatively simple device. The twocomponents creating the clamping effect are a capacitor, followed by a diode inparallel with the load. The clamper circuit relies on a change in the capacitor’s timeconstant; this is the result of the diode changing current path with the changing inputvoltage. The magnitude of R and C are chosen so that is large enough to ensurethat the voltage across the capacitor does not discharge significantly during the diodes"Non conducting" interval. During the first negative phase of the AC input voltage,the capacitor in the positive clamper charges rapidly. As Vin becomes positive, thecapacitor serves as a voltage double; since it has stored the equivalent of Vin duringthe negative cycle, it provides nearly that voltage during the positive cycle; thisessentially doubles the voltage seen by the load. As Vinbecomes negative, thecapacitor acts as a battery of the same voltage of Vin. The voltage source and thecapacitor counteract each other, resulting in a net voltage of zero as seen by the loadPart 2 Clamping circuit : Basic operationThe schematic of a clamper reveals that it is a relatively simple device. The twocomponents creating the clamping effect are a capacitor, followed by a diode inparallel with the load. The clamper circuit relies on a change in the capacitor’s timeconstant; this is the result of the diode changing current path with the changinginput voltage. The magnitude of R and C are chosen so that is large enough toensure that the voltage across the capacitor does not discharge significantly duringthe diodes "Non conducting" interval. During the first negative phase of the AC inputvoltage, the capacitor in the positive clamper charges rapidly. As Vin becomespositive, the capacitor serves as a voltage double; since it has stored the equivalentof Vin during the negative cycle, it provides nearly that voltage during the positivecycle; this essentially doubles the voltage seen by the load. As Vinbecomes negative,the capacitor acts as a battery of the same voltage of Vin. The voltage source and thecapacitor counteract each other, resulting in a net voltage of zero as seen by theload. 14
  15. 15. CONCLUSIONpart AFrom that experiment we can conclude the diode can change the AC input to theDC output. Because the diode just allows current flow to it just in one directiononly. How we know in this experiment we find many type of rectifier such as half-wave rectifier circuit like in figure 5.1, center tap full-wave rectifier circuit like infigure 5.2 and full-wave bride rectifier like in figure 5.3, every circuit are given thedifferent type of output voltage supply and different type of output wave form andthis experiment we also get how to use oscilloscope and multimeterbetter. Thisexperiment we also know with is the best rectifier. And the best rectifier is full-wave rectifier.Part BFrom both experiment we can conclude the diode can become insulator when inreverse biased and also can be a conductor when in forward biased because that’stime the resistance become low and can make the current easily flow trough diode.In this experiment also we know the how to differentiate the clipping circuit andclamping circuit just look at the circuit for example the clipping circuit the load isin series with the diode and the clamping circuit is the load is parallel with thediode. This experiment we know the clipping and clamping circuit are function tocut the signals peak. 15
  16. 16. REFERENCEInternet http://sleepycity.net/troublemakers/diodehttp: http://www.electronickitsbychaneyelectronics.com http://penang.i-learn.uitm.edu.my http://www.scribd.com/ http://nuclearpowertraining.tpub.com/ http://metroamp.com/wiki/ http://www.allaboutcircuits.comBooks Laboratory manual Fundamentals of electric circuit 16

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