active filters

Discussion in 'The Projects Forum' started by mehtab102, Dec 7, 2011.

  1. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    i want to make active filters
    1.low pass filter
    2.high pass
    3. band pass
    4.band stop

    plz help me with circuit diagram and with ic's
     
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
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  3. crutschow

    Expert

    Mar 14, 2008
    12,995
    3,229
    If you want a filter than will do the first four types of response simultaneously with one configuration you could use a biquad type.
     
  4. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    what is this??
    plz tell me the right way.
    i have 4 difrnt filters.
    can i use 741 for all.???
     
  5. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    its my class project i have to submit these with in 2 days
    plz help me
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here is a very helpful design reference guide:
    http://www.ti.com/lit/an/slod006b/slod006b.pdf
    "Opamps for Everyone"
    Active filter design techniques are covered in Chapter 16; there are 63 pages to read.

    You need to work out the calculations yourself, and show your work, or your instructor will likely give you a low grade.

    You can check your work by using this online filter design calculator:
    http://www.ti.com/tool/filter-designer
     
  7. JingleJoe

    Member

    Jul 23, 2011
    185
    10
    Why do so many people seem to do this? Leave things to the last second and/or say they'll do something they know nothing about. :confused:
     
  8. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    What do u mean thst ur instructor will mark me low grade????
     
  9. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    A.A,
    i want to shear that this account is not using by single person.all my class fellows using this site by my account...so sory to all...acctually the person who shear this last post who wants to know that in active filters how to find the the cap, and resister value for all low pass ,high pass band pass and band stop...
    this was the question...but he didnt explor his question.he told me to find out.then i open ths site and read ur comments..once again sorry to all.plz help him.
    thnx!
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Accounts are not supposed to be used by multiple people.

    Each person should have their own account. It is not that difficult to register for one. Having multiple people on the account makes things very confusing.
     
  11. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    sorry sgtwookie
    is their any solution for his q??
    and he told the cut of freq. is 80khz.
    waiting for ur response
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Certainly there is a solution - but you won't get there with a 741 opamp; as they are far too slow for 80kHz. You would be lucky to get 10kHz out of a 741.

    He will need a better opamp.
    He will also need to read through the design guide that I posted a link to, and check his work using the calculator I linked to.

    I'm not going to do it for him, as that would defeat the entire purpose of him learning how to do it.
     
  13. mehtab102

    Thread Starter Member

    Jun 21, 2011
    62
    0
    I made the circuit but graph is not like low pass...
    its a passive...
    fig atached .plz check it,...
     
  14. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Folks, if you have a problem with some one please move on, no personal attacks. I have moderated a post here because it was over the top. This site will be friendly to everyone.

    To the OP, the subject you working on is quite complex. Whole books have been written on the subject. I have researched the subject deeply, and do not consider myself expert on the subject.

    However, a couple of things stand out.

    The term you are looking for is "active filters". Your first post shows you know this, but stick with the phrase and Google it, you will get many hits. There are many, many types of filters.

    Even within the description of active filters you will find many types of filters. A simple integrator/differentiator are 1st order filters. They are very simple, one op amp, two resistors, and a capacitor. It goes up from there, with many many different kinds and curves.

    Pick a type, draw and post a schematic, and ask your questions. Because this subject is so complex you can dance around the subject forever and not get any answers unless you have specifics.

    Wookie is right on several fronts.

    Make your own account. It is not hard, so there is no excuse for sharing accounts.

    The 741 is a beginners part. It is hard to destroy (but I did it several times when I was in college), it is very limited (which is good for a teaching part, you can see what the limitations of an op amp are), and it is cheap.

    If you MUST use a 741 then use very low frequencies to play with. Stick with under 5Khz. Otherwise find an op amp that can go much higher frequencies for practical active filter applications.
     
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