KVL confusion

Discussion in 'Homework Help' started by uzair, Jan 8, 2008.

  1. uzair

    Thread Starter Active Member

    Dec 26, 2007
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    [​IMG][/URL][/IMG]


    I have inserted an image which is showing a method i employ to solve circuits through KVL.Someone please tell that is there any problem in it?

    Its quite urgent........
     
  2. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    i dont find anything wrong in it.
    do u think there is anything wrong?
     
  3. uzair

    Thread Starter Active Member

    Dec 26, 2007
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    If you see my other thread which i have posted in the general electronics section titled "applying KVL to the transistor amplifier circuit", you will find out what is the problem.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Greetings uzair,

    Like recca02, I too see nothing incorrect about your method nor your results. Can you decribe what it is about the method you have used that has you concerned?

    hgmjr
     
  5. uzair

    Thread Starter Active Member

    Dec 26, 2007
    110
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    [​IMG][/URL][/IMG]

    This diagram shows transistor amplifier circuit.The thing which is bothering me is the fact that they have used the batteries instead of "current dependent current sources",and applied the method which i have used above to deduce the result.hgmjr said that it cannot happen.That is the problem.

    Note:I have not mentioned input and output terminals,the input is at extreme left and the output is at extreme right.
     
  6. hgmjr

    Moderator

    Jan 28, 2005
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    Here is a sketch of the transistor model that I would use to write the KVL equations for the CE stage in you provided. It should be suitable for DC analysis.

    hgmjr
     
  7. uzair

    Thread Starter Active Member

    Dec 26, 2007
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    Where is the transistor????!!!!....:confused:
    In another book,they have applied KVL equation only to the output loop,the result was:-
    Vce = Vcc - IcRc
    Is it right?
     
  8. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    The components inside the dash-outline are the mathematical representation of a transistor. That is why it is called a model. Models similar to this one although a bit more complex are used in PSPICE and other circuit analysis programs to simulate the electrical behaviour of a transistor.

    For example, looking at the left side of the diagram you see the Vbb input voltage source from your diagram. Then you see in series with Vbb, the base resistor Rb. Then you encounter the intrinsic diode resistance R-sub-pi. Then you encounter a voltage source that accounts for the foward biased base emitter junction Vbe. If you treat the contents within the dashed lines as a black box, the input and the output would behave in much the same way as a transistor.

    This is a mathematical model so it can be used to calculate the output voltages and currents as a function of the input voltages and currents. KVL will work on these circuit elements.

    hgmjr
     
  9. uzair

    Thread Starter Active Member

    Dec 26, 2007
    110
    0
    Thanks a lot sir.It will be of great help.Thanks again!
     
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