Band-pass filter problem

Discussion in 'Homework Help' started by davva, May 9, 2013.

  1. davva

    Thread Starter New Member

    May 9, 2013
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    Hey yall !
    I've got quite the problem with an assignment related to designing a band-pass filter.

    In the assignment i have to design a band-pass filter which filters out a specific frequency, 5 k Hz. I have uploaded a jpg of the circuit I'm using. The assignment spec gives the choice of using an inductor/coil with either 100 μH or 220μH. After choosing the coil with the inductance of 100 μH i used the equation, seen in the attachments, to calculate the capacitance.

    The circuit works as intended but ....

    As i re-read the assignment spec i discovered that the coil also has a "natural resistance" of 0.21 Ω resp. 0.43 Ω (for the coils with 100 μH and 220μH).
    When i applied the resistance to the circuit the result was of course not at all as good as before.

    So my question is ... What do i need to do in order to compensate for the resistance of the coil to get the "same" result as before introducing it ?
     
  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    Post the assignment spec.
     
  3. davva

    Thread Starter New Member

    May 9, 2013
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    The assignment spec is not in English, which is why i didn't post it. What kind of additional information were you looking for ?

    I Should say that i have tried finding an equation which takes the coils resistance in to consideration but so far i have been unsuccessful. I'm not sure if i need to redesign the circuit entirely or if adding some component is enough, like a opamp perhaps ?
     
  4. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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    You obviously speak English, and presumably the other language as well.

    Post the English translation of the spec.

    The usual sorts of specs; allowable attenuation at the center frequency, required out of band attenuation, etc.

    That shouldn't be too difficult.

    No single passive component is going to fix the problem. You could add a fixed gain equal to the loss at the center frequency.
     
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    It's been decades for me since I was in school. All real coils have some resistance which degrade their performance compared to ideal coil. If you are using a simulator, you may want to experiment with adding a "peaking capacitor" at various places to see if you can peak up the response a little.
     
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