Decoders

Discussion in 'Homework Help' started by cheyenne, Mar 5, 2008.

  1. cheyenne

    Thread Starter Active Member

    Dec 6, 2007
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    0
    I am having problems with the following question:

    Using two 3-8 decoders, design a circuit to perform the following function.

    F(A,B,C,D) = ∑(0,4,6,14)

    Is anyone able to show me what to do here. I am finding decoders quite a tricky topic. Please help. Can anyone also explain how to solve the problem?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    A decoder like a 74LS137 simply uses the three bit input to enable one of eight outputs. Get the data sheet for one to see how it's done.
     
  3. cheyenne

    Thread Starter Active Member

    Dec 6, 2007
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    0
    The question I have posted asks for 4 inputs. How is this done if a decoder only has 3 inputs?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    Possibly one decoder can use three inputs, and the fourth plus two others can feed the second one.
     
  5. dogar sahab

    Active Member

    Mar 15, 2008
    116
    0
    you must search the topic DECODER EXPANSION....decoder expansion is all about how to construct 4-16 decoder from 3-8 decoder.....after reading this you will be aware of the intricacies by yourself....
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    Most decoders/encoders have a disable pin, that is the key.
     
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