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Predicting AC open-loop gain for an internally compensated op-amp

  1. Sep 26, 2016 #1
    1. The problem statement, all variables and given/known data
    An internally compensated op amp has a DC open-loop gain of 1,000,000 (V/V) and an ac open-loop gain of 40dB at 10kHz. Provide the expected gain in dB at 1kHz...

    2. Relevant equations
    Please help, I don't know what to use for an exact answer.

    3. The attempt at a solution
    Beyond the break-point, the gain goes down as frequency goes up. So I just picked the value larger than 40dB (since the frequency decreased).
     
    Last edited by a moderator: Sep 27, 2016
  2. jcsd
  3. Sep 27, 2016 #2

    berkeman

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    Staff: Mentor

    How many poles does an internally compensated opamp typically have, and where located? So what would you expect the rolloff to be in the 10kHz to 1kHz region?
     
  4. Sep 27, 2016 #3
    What? Is there another word for poles or rolloff? I don't know what these mean.
    Is my intuitive answer usually how this problem would be answered?
     
  5. Sep 27, 2016 #4

    berkeman

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    Staff: Mentor

    What class are you in? What textbook are you using? What have you found when you use the very helpful Internet to search for information on Dominant Pole Compensation for Opamps?
     
  6. Sep 28, 2016 #5
    302 Analog electronics
    https://www.uwplatt.edu/files/colla... ENGINEERING TECHNICAL ELECTIVES.4.14-2_0.pdf

    Microelectronics 4th edition by Neamen

    Thank you for giving me a precise phase to search and learn about:
    https://en.wikipedia.org/wiki/Operational_amplifier#Frequency_compensation
    half-power frequency = 3dB down frequency vs the unity gain frequency...(Note to self - Lab Design project #1 III. Measurements, Amplifier gain)
    http://www.ti.com/lit/an/sloa020a/sloa020a.pdf#page=19
    http://web.mit.edu/klund/www/papers/ACC04_opcomp.pdf

    I have to go, but I will come back and read more about this...
     
  7. Sep 28, 2016 #6

    berkeman

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    Staff: Mentor

    You are heading in the right direction, but just saying the gain is "greater" is not an answer to the question
    Answering those questions will give you the quantitative answer... :smile:
     
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