test bandpass

Discussion in 'Homework Help' started by sunone, Jan 17, 2011.

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  1. sunone

    Thread Starter New Member

    Jan 11, 2011
    I have to build a bandpass filter, noise filtering and removing the DC component for a signal, the range is [0.5-5 Hz].

    I am using the following design:

    Considering my available components (but I am planning
    to use more coherent stuff)
    Part high-pass:
    C1, C2 = 1 microF
    R1 = 450 KOhm
    R2 = 225 kOhm
    Part lowpass:
    R1, R2 = 8.2 KOhm
    C1 = 4.7 microF
    C2 = 2.2 microF
    -------------------------------------------------- --------------
    Here are my questions,
    1. Using a wave generator and an oscilloscope, how do I test that the allowed band is effectively [0.5-5 Hz] ? What differences should I see if I send as an input a square/triangle/pseudo-sinus wave inside and outside the band ?

    3. I need to avoid dual supply amplifier, 'cause the rest of the circuit is aa single supply. Assuming I have some LM386 and LM358, is it correct to just use the bottom circuit in the picture I posted ?

    4. Considering I want to filter a signal coming from a photodiode and a transimpedence amp. removing noise and DC component. Can I stick with the filter I posted, or should I investigate more about Butterworth, Bessel and so on filter .... ?
    Last edited: Jan 17, 2011
  2. sunone

    Thread Starter New Member

    Jan 11, 2011
    Can I kindly receive an explanation why my questions were moved in HOMEWORK HELP ???!?!?!!?
    I can understand that for some of you some of these questions are really easy but for me they are not!!!!!!!
    And browsing among the threads I don't see a big difference between my questions and the questions of the other users!!!! I FOUND THIS BEHAVIOUR REALLY OFFENSIVE.:mad::mad::mad:

    After a Msc in Informatic Engineering and a Ph.d in Applied math for medical imaging, I don't expect to be a genius of electronics because it is just an hobby and I am here to learn. But I found difficult to learn if someone discriminates me for some reasons. Is there a not clear motivation in the rules of the forum ? Can I have explained which part of the forum agreement did I violate ?

    Best regards
  3. bertus


    Apr 5, 2008
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    As you are experienced in math. Take a look at this book http://focus.ti.com.cn/cn/lit/an/slod006b/slod006b.pdf Feel free to ask anyway if you have some problems
    sunone likes this.
  5. Georacer


    Nov 25, 2009
    I don't see any other physical way to test this appart from actually using a signal generator and an oscilloscope. Both very expensive equipment, unless you 're lucky and have access to a laboratory's equipment.

    The simulation is a much more reliable method of theoretical study, though.
  6. sunone

    Thread Starter New Member

    Jan 11, 2011
    Thank you for your reply.
    If you read my first question in the post, I am actually asking a specific question assuming that I have these instruments in my apartment and my lab:

    - Assuming I have a wave generator and an oscilloscope.
    - If I send to the input of the bandpass filter a square wave outside a the allowed frequency. What should I see if the circuit is working properly ?
    I assume nothing. If I see some micro-pseudo sinusoide is it still acceptable or this means I have done some mistake in the design? This is what I meant in the original question, sorry if it was not clear.

    Not really, I am sure you can find some cool and in good condition Tektronix even on Ebay :) :) for less than 1000 euro. Take a look :)
    About the wave generator, even the good one are no more than 100-300 Euro. And you can find also good stuff for less than 100 Euro, depending what you need.
    Last edited: Jan 17, 2011
  7. sunone

    Thread Starter New Member

    Jan 11, 2011
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