Can someone explain why it's wrong: Inveri

Discussion in 'Homework Help' started by Hayaalsh, Feb 21, 2014.

  1. Hayaalsh

    Thread Starter New Member

    Mar 23, 2013
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    Hi.
    I have a question.. Why we cant use voltage divider rule instead of source transformation?
    I attached a photo of the problem..
    I wish someone explains!

    Thanks alot
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    The 50k loads the voltage divider and is effectively in parallel with the 20k.
    It's possible to use voltage divider if you keep the aforementioned in mind.
     
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  3. Hayaalsh

    Thread Starter New Member

    Mar 23, 2013
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    Thats right! Thank you..
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Did you understand why tnk said that?

    It is because the input of the op amp is virtual earth.

    It is often forgotten in op amp circuits that the inputs are (biased) at earth potential.
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    Commonly done for op amp inverting circuits, not for non-inverting circuits.
     
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  6. Hayaalsh

    Thread Starter New Member

    Mar 23, 2013
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    what would happen if the op amp input was not 0V?
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    At "earth" potential?

    Huh?

    So just how is this accomplished?
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
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    OK so it was badly phrased, and I really meant zero. I also should not really have said biased since it is the opamp's gain that causes this.

    Perhaps you would like to formalise it.
     
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