Differential input differential output ,butterworth LC Low pass active

Discussion in 'Wireless & RF Design' started by arunkuttath, Oct 5, 2015.

  1. arunkuttath

    Thread Starter New Member

    Oct 5, 2015
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    i want to implement a filter , butterworth filter with LC active circuitry.
    Please tell me how to implement it . i also want to input and outputs signals in differential mode. So the chance is an active filter
    Thanks in advance
    Arun
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Active filters do not generally use inductors. You need to do some basic research before we can move forward. Please acquaint yourself with the circuit known as a Sallen-Key filter. Cascading 1st and 2nd order sections is how filters of higher order are constructed.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    High-pass, Low-pass, Band Pass?
    Cut-Off Frequencies?
    Input/Output impedance?
    Signal/Power levels?
     
  4. arunkuttath

    Thread Starter New Member

    Oct 5, 2015
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    thank you all
    i want a general solution for the butterworth or sallen-key etc. But the circuit must be a LC circuit.
    I just want what are the things that i want to consider ? please post some pdf or other design guidelines that can satisfy my requirement.
    regards
    Arun
     
  5. Papabravo

    Expert

    Feb 24, 2006
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    We don't know what your requirements are. You mentioned "LC active circuitry", but I suspect you have no idea what that implies.
    In order to design ANY kind of filter you need to decide:
    1. Where is the passband
    2. How much ripple is allowed in the passband
    3. Where is the stopband
    4. How much ripple is allowed in the stopband
    5. What rolloff is required in the transition band
    From this information we can determine the required order of the filter and then we can talk about weather it consists of passive components, L's and C's, or active components like opamps, R's and C's.

    You might find the following references helpful
    http://www.crbond.com/papers/btf2.pdf
    https://sarviechousite.files.wordpress.com/2014/04/analogue_filter_design.pdf
     
  6. MikeML

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  7. arunkuttath

    Thread Starter New Member

    Oct 5, 2015
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    thank you all,
    but there is nothing with the differential filters.
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    In point of fact, in a career spanning half a century, I've never seen anything on this subject either. I suppose one could design a standard filter with differential to single-ended conversion on the input and single-ended to differential conversion on the output.

    BTW - Differential signals are normally used for data transmission. The fast edges are rich in harmonics and a filter would only distort the waveform with possibly unintended and disastrous consequences. I'm thinking that filtering ANY differential signal makes no sense at all. The constant refrain is "Don't let the eye close". Maybe you are working with something we mere mortals cannot comprehend and so a bit of background might be helpful.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the term is ballanced, in rf filters there are unballanced, one side grounded, and ballanced filters. look up ballanced filter design.
     
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