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Homework Help: Diode and c.r.o. question

  1. Nov 7, 2005 #1
    i have to draw the c.r.o. display for a diode, is it just the same as for an a.c. input but with the parts that were below the x-axis, intead reflected in the x-axis?
     
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  3. Nov 7, 2005 #2

    Ouabache

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    I don't quite follow you.. Are you supplying AC to a diode (and hopefully a load resistor) and looking at the time varying characteristics of voltage on a scope? Or are you interested in the voltage versus current charateristics of the diode which can be measured with a curve tracer? (See second to last row for diode examples)
     
  4. Nov 8, 2005 #3
    i assume that i have a circuit with a diode in it, connected to a c.r.o., and i have to draw the voltage/time shape that it would produce. e.g. for mains ac you would get a sinusoidal wave form - that's the kind of setting i'm on.
     
  5. Nov 8, 2005 #4

    Integral

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    What is a c.r.o. ?
     
  6. Nov 8, 2005 #5

    andrevdh

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    The signal will be clipped on one side, this is actually when the diode is conducting - it's resistance is low. In the attachment the zero voltage level is the dotted line.
     
    Last edited: Nov 29, 2006
  7. Nov 8, 2005 #6

    Ouabache

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    c.r.o. - cathode ray oscilloscope

    andrevdh that's right, only one half of the cycle would be displayed, the other half is clipped. (though on yours, it appears, there was a negative dc bias applied as well).
    QueenFisher, can you guess what a diode in this configuration, is also called?
     
    Last edited: Nov 9, 2005
  8. Nov 9, 2005 #7

    andrevdh

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    What I am try to indicate is that the diode needs a bit of bias (depending on the type of diode) before it starts to conduct. It does not conduct straight away.
     
  9. Nov 9, 2005 #8

    Ouabache

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    Why is it a negative DC bias? What are some example magnitudes for turn-on voltage of a diode (Ge, Si, PIN) ?
     
  10. Nov 14, 2005 #9

    andrevdh

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    It just depends on which way round you connect the diode or the oscilloscope in the circuit. I could just as well have drawn the mirror image of the diagram. The forward voltage drop is usually of the order of 1 volt (0.6 for silicon diodes).
     
  11. Nov 14, 2005 #10
    yeah it depends really
     
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