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op amp circuit

Discussion in 'Electronic Basics' started by aabid, Jun 6, 2005.

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  1. aabid

    aabid Guest

    I require a Single Op-Amp Bandpass Filter circuit with a gain of 100X
    and the frequency range is 0.1 Hz to 45 Hz.

    I found a circuit in the following website:

    http://ourworld.compuserve.com/homepages/Bill_Bowden/opamp.htm

    According to specs, the Q factor must be greater than the square root
    of half the gain. But as you can see my requirements do not meet with
    this condition. Hence, please help me out here.

    Thanks.
     
  2. Ban

    Ban Guest

    This circuit will do what you want,but requires a big capacitor on the
    input. If you use a dual opamp like the NE5532 you need the same space but
    can reduce the cap by a factor of 100 or more. The noise will go up tho.

    ||
    .----||--.
    | 3n3|| |
    \] ___ | ___ |
    o---|]--|___|--o--|___|-o
    /]+ 11k | 1M1 |
    150u | |\ |
    '--|-\ |
    | >--o---o
    .--|+/
    | |/ NE5534
    ___ | ___
    GND-|___|-o-|___|-VCC
    22k | 22k
     
  3. Ban

    Ban Guest

    This circuit will do what you want,but requires a big capacitor on the
    input. If you use a dual opamp like the NE5532 you need the same space but
    can reduce the cap by a factor of 100 or more. The noise will go up tho.

    ||
    .----||--.
    | 3n3|| |
    \] ___ | ___ |
    o---|]--|___|--o--|___|-o
    /]+ 11k | 1M1 |
    150u | |\ |
    '--|-\ |
    | >--o---o
    .--|+/
    | |/ NE5534
    ___ | ___
    GND-|___|-o-|___|-VCC
    22k | 22k
     
  4. Bob Masta

    Bob Masta Guest

    A frequency range of 450:1 is way too large for a simple
    bandpass filter. You should have separate low-pass
    and high-pass stages for this.

    Best regards,


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Home of DaqGen, the FREEWARE signal generator
     
  5. I think you should think in terms of a dual opamp and a 10X high pass
    filter (2 or 3 poles) followed by a 10X low pass filter (2 or 3 poles).

    You might download a free copy of this little filter design aid to
    play around with variations.

    http://www-s.ti.com/sc/techzip/slvc003.zip
     
  6. colin

    colin Guest

    that page doesnt give the single op amp sallen key bandpass filter, wich u
    might look at as an alternative, the one shown is a multiple feedback type.

    try this calculator ....

    http://www.analog.com/analog_root/static/techSupport/designTools/interactiveTools/filter/filter.html

    Colin =^.^=
     
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