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bandpass filter

Discussion in 'Electronic Design' started by John, Sep 28, 2003.

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  1. John

    John Guest

    hello I need a schematic of bandpass filter of 14.5 khz. If anyone can help thanks.
     
  2. WE need to know a lot more about the details to give any useful advice
    (what bandwidth, in band ripple, out of band rejection, active or
    passive, what supplies are available, must this filter pass
    significant power, etc.) But if you want to read into some active
    filter possibilities, look at:

    http://www.national.com/an/AN/AN-779.pdf

    At this frequency range, I like the biquad, 3 opamp design for
    stability and adjustability.

    http://www-k.ext.ti.com/SRVS/Data/ti/KnowledgeBases/analog/document/faqs/ssbqbphq.htm
     
  3. Ban

    Ban Guest

    Here is a small circuit, which allows tuning with a single resistor R3,
    while maintaining gain and bandwidth.

    design equations:
    fr= 1/(2*pi*C) sqrt((R1+R3)/(R1*R2*R3))
    gain: -Ar=R2/2R1
    Q= pi*R2*C*fr
    B= 1/(pi*R2*C)
    +--------+--------+
    | .-. |
    --- | |R2 |
    --- | | |
    |C '-' |
    ___ | || | |\ |
    o-|___|-+---||---+---|-\ |
    R1 | ||C | >-+--o
    | +--|+/
    .-. | |/
    | |R3 ===
    | | GND
    '-'
    |
    ===
    GND
    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    ciao Ban
     
  4. Ban

    Ban Guest

    hello I need a schematic of bandpass filter of 14.5 khz. If anyone
    forgot to mention that the operational amplifier needs a open loop gain of
    greater than 2*Q^2 at the resonance frequency. This is particulary difficult
    to obtain for higher values of Q. On the other hand the circuit is pretty
    immune against self_oscillation at fr even with components not exactly the
    calculated value.
    Of course a must is the right bypass and frequency correction of the opamp
    to avoid high frequency oscillations.

    ciao Ban
     
  5. Brian

    Brian Guest

    John,
    While you didn't supply a lot of needed information, I will give you two examples of
    circuits (with their response curves). If you will give more information, then we can
    give you a circuit to match your needs. See the circuits at
    http://www.fncwired.com/BandpassExample
    hope this helps,
    Brian
     
  6. Jim Thompson

    Jim Thompson Guest

    See "GyratorFilterBP.pdf" on the S.E.D/Schematics page of my website.

    ...Jim Thompson
     
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