Second order low pass filter with unity gain

  • #1
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Homework Statement


I need to design a second order filter with unity gain.

Homework Equations


None - not taking component values into account for now.

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
 

Answers and Replies

  • #2
NascentOxygen
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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?
 
  • #3
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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.
 
  • #4
NascentOxygen
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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.
 
  • #5
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How would I go about changing that?
 
  • #6
NascentOxygen
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How would I go about changing that?
Do you need it to be any different, though?

For flatter responses, google: active filters.
 
  • #7
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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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