# De-Morgans law / Nand gates.. I'm left a bit confused

Discussion in 'Electronics Homework Help' started by thepipersson1980, Jul 21, 2014.

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Jul 21, 2014
Hi guys and girls,

Ok so I'm doing a course at the moment which is left me a bit confused around the whole NAND gate's. the course it's self only has seven pages on this topic (helpful), so I have scoured the internet to try and find an explanation so I can work out the answer but as said it has left me most confused.

This is the Question;

In addition to this they would like more advanced users to learn how to use De-Morgan's law.

(A+B).(A+C)

Show how can this be implemented using NAND gates using De-Morgan's law.

Now I'm not asking for the answer just maybe point me in the right direction of where I can get help for this please!

This is what I can work out so far;

So .is AND
+ is OR
Overbar is logical NOT
De-morgan’s law
"not (A and B)" is the same as "(not A) or (not B)"
"not (A or B)" is the same as "(not A) and (not B)
But after scouring the net it doesn't seem to have any not's is there, maybe overbars missing? OR is it the fact that a NAND gate is a mixture of a AND gate and a NOR gate and not a NOT gate???
I'm at my wits end with this one, I'm not sure if I'm just trying to make something that is not there.... and where is the logic in this? lol
Any help will be much appreciated
Thanks

2. ### Gryd3

4,098
875
Jun 25, 2014
NAND - Not AND
NOR - Not OR

The difference is the inverting output.
(A and B) = AND (Both A and B must be true for the output to be true)
NOT(A and B) = NAND (Both A and B must be true for the output to be false)

4
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Jul 21, 2014
Ok that makes sense... do you know anywhere where I can get some simple research tips please?

4. ### Gryd3

4,098
875
Jun 25, 2014
I don't have anything readily available unfortunately. If I were to provide something, it would be a result or two from doing a google search.
I'd encourage you to do more searching, and ask more questions when you hit a road block.
Someone else may have a resource they enjoy. We'll have to hang around a little longer for them to reply.

5,164
1,087
Dec 18, 2013
I don't know if this is what you mean, gate functions like AND, OR, and NOT can be made from just NAND gates. A not gate is made by joining the two inputs of the NAND together (NOT NAND). AND is made by a NAND and a NOT NAND on the output. An OR is made by two NOT NAND gates on the input of a NAND one on each pin.

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Jul 21, 2014
Ok thanks for the replies guys and sorry for the late response I will check back tomorrow as I now have to go to work

7. ### Ratch

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Mar 10, 2013
Implementing any logic circuit with all NAND or NOR gates is a cut and dried process that just about any good logic book can show. The program in the attachment breaks down a logic expression into minterms. This enables you to see if your new implementation matches the original problem. Be sure to peruse the "readme" file.

Ratch

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