Quick NAND gate problem

Discussion in 'Homework Help' started by Enzo, Nov 14, 2008.

  1. Enzo

    Thread Starter New Member

    Nov 14, 2008
    1
    0
    Hey guys, I've got a quick question concerning NAND gates, but I think my entire fundamentals on this subject is a bit shaky...

    I've attached the problem

    If im not mistaken, a NAND gate works opposite to an AND gate, whereby it produces a low (or, 0) when both inputs are high.

    Which means if in the example, NotA and NotB would actually produce 0? Why does it say that it produces Not(NotA*NotB)?
     
  2. hobbyist

    Distinguished Member

    Aug 10, 2008
    764
    56
    Remember The output is opposite the input.
    Which means is if the inputs are "NOT A * NOT B" then the output has to be the opposite of it which means is it is NOT "NOT A * NOT B"..

    The key is , whatever the input is wether it is a high or a low the output will be the Exact OPPOSITE.
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    A NAND gate's output is (AB)', where ' means not or bar or inverted.

    If you put a NOT gate on each of the inputs then it becomes

    (A'B')' as the diagram shows (if you use De Morgans rules you will see that this function is actually an OR gate!).
     
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