Designing bandpass filters for harmonics Project

Discussion in 'The Projects Forum' started by PMB917, Mar 7, 2006.

  1. PMB917

    Thread Starter New Member

    Mar 7, 2006
    5
    0
    I'm putting together a project for school (ITT Tech Woburn MA) that deals with harmonics of certin tyes of waves. (square, triangle,sawtooth ect.) I need to design variable gain bandpass filters for 2kHz, 4kHz, 6kHz, 8kHz and 10kHz.

    There are a few ways to do this, and I've found one way to do this with only one op amp.

    http://www.elecdesign.com/Files/29/4481/Figure_01.gif

    The only problem here is that they dont give any formulas for setting the center frequency or Q.

    Anyone farmilure with this design?

    I also had another thought to use a multiple feedback bandpass filter design.
    http://www.captain.at/electronics/active-filter/
    But that would mean I'd need twice the number of op amps to be able to vary the gain.

    I could go sallen key but then I'd be upto 3 op amps per harmonic totaling 14 and theres only so much room on a breadboard.


    anyone got suggestions?
     
  2. CoulombMagician

    Active Member

    Jan 10, 2006
    37
    0
    Try a switched cap filter( see linear tech website for ICs). The center frequency is proportional to the clock frequency which can be varied easily. You need a filter circuit with a fixed bandwidth that is independent of the cneter frequency however.
     
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