How does a 74LS47 works basically?

Discussion in 'Homework Help' started by zener_16, Feb 8, 2010.

  1. zener_16

    Thread Starter New Member

    Feb 1, 2010
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    i read the datasheet of the 74LS47 but cant really understand how it works..
    i just know that it is a BCD to 7 Segment decoder..
    anyone can tell me more about 74LS47 function?
    Ty.
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    Which part of the function do you not understand?
     
  3. zener_16

    Thread Starter New Member

    Feb 1, 2010
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    how does it works basically? A very general one.
    like why is it active-low at the outputs?
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    7447 is is a simple IC that "converts" BCD code to LED 7-SEGMENT display.
    And 7447 is design to driving command anode LED displays. And that is why we have active-low at the outputs.
    http://en.wikipedia.org/wiki/Binary-coded_decimal
    http://en.wikipedia.org/wiki/Seven-segment_display
    And see the TRUTH TABLE
    http://maven.smith.edu/~thiebaut/270/datasheets/sn74ls47rev5.pdf
     
    Last edited: Feb 8, 2010
  5. Papabravo

    Expert

    Feb 24, 2006
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    Each segemnt of the display has associated with it a Boolean equation that determines weather the segment is on or off. For a single digit there will be seven equations, with each equation using four inputs. The equations can be written as a Sum of Products (SOP) or as a Product of Sums (POS) depending on which is easier to implement.

    Here is the important point. A decoder is a combinatorial circuit with NO memory elements.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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  7. nodoubtman

    New Member

    Oct 21, 2011
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    Hi! What's the difference between 74ls47 and 7447 ic??

    thank you!
    good evening!
    marC:)
     
  8. BillB3857

    Senior Member

    Feb 28, 2009
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    Have you looked at the spec sheets of each? No better way to learn!
     
  9. tshuck

    Well-Known Member

    Oct 18, 2012
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    No doubt that this is a resurrection!

    Post a new thread if you need a question answered, not highjack a two year old one :D
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    The LS device has less drive capability and the inputs represent a smaller load. It's all in the datasheet. Get them, read them, and appreciate them!
     
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