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problem with op amp positive and negative feed back at a time?

Discussion in 'General Electronics Discussion' started by chaitanya2k6er, Dec 9, 2010.

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  1. chaitanya2k6er

    chaitanya2k6er

    3
    0
    Dec 9, 2010
    hi!!
    I got stuck up with the op amp circuit which has both the positive and negative feed backs? What is the use of using op amp with both feed backs at a time? How to analyze the circuit? Please suggest me the solution with the required formulas.
    Thank u..
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
    2,718
    Jan 21, 2010
    Do you want to post a link to the schematic?

    And why do you want the circuit explained (it may help us in formulating a suitable reply)?
     
  3. chaitanya2k6er

    chaitanya2k6er

    3
    0
    Dec 9, 2010
    i have attached the circuits related to this.
    no specific reason, i want to implement the circuit for some application.
     

    Attached Files:

  4. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    The basic technique for analyzing an op-amp circuit is to calculate the voltage at the (-) input to the op-amp as a function of the output and/or input voltage. Then do the same for the (+) input. Set these two expressions equal to each other, V(-)=V(+), then crank the algebra to get the output voltage as a function of the input voltage. So if I did the algebra right, the answer is Vo = V1(R1R4+R2R4)/(R2R4-R1R3).
     
  5. chaitanya2k6er

    chaitanya2k6er

    3
    0
    Dec 9, 2010
    thank u..
    but i have not understood what you have suggested. Could you please elaborate it.
     
  6. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    Just write the node equations at the op-amp inputs, then solve for the output voltage as a function of the input voltage. See attachment.
     

    Attached Files:

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