Buffered Band-pass

Discussion in 'General Electronics Chat' started by Shagas, Sep 17, 2013.

  1. Shagas

    Thread Starter Active Member

    May 13, 2013
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    Hello ,

    I want to make an adjustable bandpass filter for a 0-5volt audio signal.

    The low-pass will be adjustable from about 30-200hz and the high pass from about 1000-5000hz.

    I'm planning to do something like this

    http://www.electronics-tutorials.ws/filter/filter_4.html

    But i'm planning to add a unity gain op amp buffer(powered by 9v) between the two stages and on the output aswell so In total two buffers.
    Two pots will be adjusting the bandpass frequencies .

    I've calculated my high pass to be 100nf and 5k-50k variable resistance and for the low pass 22nf and 1k-10k variable resistance.

    What do you guys think? Is it necessary to put a buffer inbetween the stages and on the output or would it be enough to have one in between.
    The output is going to drive the wiper of a 50k pot which will go to a micro ADC.
     
    Metalmann likes this.
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I would buffer both of them. Then you don't need to worry about what the input to the ADC looks like.
     
  3. Shagas

    Thread Starter Active Member

    May 13, 2013
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    Ok thanks for the advice, ronv
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    You can using CD4066 to be the AC signal switch, to select several different bandpass filters.

    Also the CD4051 is another choice.
     
    Last edited: Sep 18, 2013
  5. Shagas

    Thread Starter Active Member

    May 13, 2013
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    yes thanks that's a good idea
     
  6. Metalmann

    Active Member

    Dec 8, 2012
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    Thanks, Shagas; that's a great site to study.:cool:
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    And is this ADC tied to (or integrated in) a MCU? If so, why not perform the filtering digitally? Eric007 can help you!
     
  8. bertus

    Administrator

    Apr 5, 2008
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  9. Shagas

    Thread Starter Active Member

    May 13, 2013
    802
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    ;)


    The ADc is an AVR adc so yes , integrated. The avr is already busy doing a load of other stuff so I didn't want to introduce digital filtering.

    Thanks for the link bertus
     
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