# 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)?

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2. ### hobbyist Distinguished Member

Aug 10, 2008
773
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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!).