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Second order low pass filter with unity gain

  1. Mar 19, 2017 #1
    1. The problem statement, all variables and given/known data
    I need to design a second order filter with unity gain.

    2. Relevant equations
    None - not taking component values into account for now.

    3. The attempt at a solution
    Is this a correct method of creating a 2nd order low pass filter with unity gain?
    New Doc 2017-03-19.jpg
     
  2. jcsd
  3. Mar 19, 2017 #2

    NascentOxygen

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    Staff: Mentor

    97838-07182a19b92ad5fea6619308e7f7ca40.jpg

    That is one such candidate; not what I'd consider a good representative of such a filter, but it certainly fits.

    What is the application you need it for?
     
  4. Mar 19, 2017 #3
    I had to design a two part system with a transimpedance amplifier then a second order low pass filter for a piece of coursework. It's specified that we cannot use a power supply larger than 5v for the opamps though, so I designed the system to take care of all of the gain during the transimpedance stage.

    Sorry if that sounds confusing, I'm still getting my head around this a little bit.
     
  5. Mar 19, 2017 #4

    NascentOxygen

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    Staff: Mentor

    What you have there is basically a passive two-stage filter, so its Bode plot is not nice and level over any range, it begins drooping right from DC.
     
  6. Mar 19, 2017 #5
    How would I go about changing that?
     
  7. Mar 19, 2017 #6

    NascentOxygen

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    Staff: Mentor

    Do you need it to be any different, though?

    For flatter responses, google: active filters.
     
  8. Mar 19, 2017 #7
    Probably not, the question wasn't particulary specific, it just asked for a second order low pass filter so that's probably fine. Thank you for your help! :smile:
     
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