CL and OL of inverting amplifier

Discussion in 'Homework Help' started by ronybhai, Sep 18, 2012.

  1. ronybhai

    Thread Starter Member

    Sep 18, 2012
    97
    0
    What is the relationship between the open-loop gain of an op-amp and the closed-loop gain of an inverting amplifier?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
  3. ronybhai

    Thread Starter Member

    Sep 18, 2012
    97
    0
  4. ronybhai

    Thread Starter Member

    Sep 18, 2012
    97
    0
    I think this formula can be used for the relationship between CL and OL
    Acl=Aol/ (1+B *Aol)
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    The closed loop gain is controlled by the external components and the open loop gain does not enter into the calculation.
     
    ronybhai likes this.
  6. ronybhai

    Thread Starter Member

    Sep 18, 2012
    97
    0
    Open loop doesnt enter into what calculation?
    Can you verify if the formula I posted above is correct?
    Thanks
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    Suppose Aol=100k, and the feedback ratio is .001. You actual gain would be ≈1% lower than the value calculated from the feedback resistor ratio. Open loop gain can usually be ignored, but you need to be aware that it is finite.
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    That is true, but we seldom have a closed loop gain that is closer to the open loop gain than say four orders of magnitude. This is like saying I write all my answers to 9 significant figures because I like to be precise.

    One of the great benefits of reducing the gain by closing the loop is the corresponding increase in bandwidth.
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    "Seldom" is the key word here. This is precisely why I said
     
Loading...