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Building a 3:8 decoder with tristate outputs

  1. Apr 16, 2013 #1
    So all my 3:8 decoders have outputs only at 1 and 0. I need a tristate decoder that can be configured so that the unused outputs are open circuits (i.e. high impedance).

    I know how to build a 3:8 decoder (using logic gates). How might I go about modifying it so that it has tristate outputs? Is this possible?

    BiP
     
  2. jcsd
  3. Apr 16, 2013 #2

    berkeman

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    Staff: Mentor

    Would be easier to just put Tri-State buffers on the 8 outputs of the decoder, no? Or is your goal to build up the 3:8 decoder circuit to learn about it?
     
  4. Apr 16, 2013 #3
    Thanks! That's actually what I ended up doing once I learned about the tri-state buffer. Do you happen to know the datasheets for the tri-state buffer?

    BiP
     
  5. Apr 16, 2013 #4

    berkeman

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    Staff: Mentor

    The '245 and '240 I think are octal Tri-State buffers. If you want slow CMOS, that would be the 74HC240 and 74HC245. If you want fast CMOS, that would be the AC or VHC families...
     
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