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
    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.

    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.
    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
    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.