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Inverting op-amp with too much gain ?

Discussion in 'Electronic Design' started by [email protected], Mar 7, 2007.

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  1. Guest

    Trying to build a multi-stage 120kHz bandpass filter... decided to
    use multi-feedback topology...

    Seems that it amplifies the desired signal alright, but ends up full-
    swing output (after just one stage) and since it's inverted, the full-
    swing output feedback ends up cancelling out the input and it
    collapses back on itself.

    I'm no op-amp expert but am ernestly trying to learn.... and I'm
    stumped on how to procceed...

    thanks!
    ...dane
     
  2. Schematic? Maybe you could shoot for unity gain in the filter stage and do
    your amplifying seperately. The filter stage will still provide gain, but
    only to what you want to hear. Download TI FilterPro, you won't regret it.
    I've built active filters using it, it works. :)
    http://focus.ti.com/docs/toolsw/folders/print/filterpro.html
     
  3. dane

    dane Guest

    Schematic? Maybe you could shoot for unity gain in the filter stage and do
    Thanks Anthony. I tried it out and it's working great...

    I used some filter design tool the first time around (can't remember
    which), but I think I may have 'tweaked' it too much and broke it...
    Going back to FilterPro helped a lot and I'm now back-on-track.

    thanks!
    ...dane
     
  4. I told ya you'd like it. :)
     
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