# Can somebody please give me some ideas.

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#### Dennisc

##### New Member
I've attached a scan of a problem I'm working on. I need to change this circuit to all NAND gates. I have no clue if what I've done so far is correct. It seems like to go to NAND you have to get rid of the +'s. Is this even close to correct the way that I've done it? Once I have converted this to a NAND circuit then I need to draw it. I would greatly appreciate any advice.
Thanks

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##### Well-Known Member
This looks like a lesson in reduction using identities and such. I notice an important reduction available in each example. The left hand figure includes the function A'+A'B. If you think about this for a bit, you may realize that this is equal to A'. Consider that if A=1, then A'=0 and the term A'B must also equal 0 (no matter what B is, a 0 ANDed with it will always be 0). If A=0, then A'=1 and the first term insures that the overall result will be 1. So basically, it doesn't matter what B is at all. So the overall equation can be reduced from A'+A'B+AC = A'+AC.

In the right hand example, I notice that we have a term DBD'. When you AND something with the inverse of itself, the result must always be 0. When you include a 0 term in an OR, it does nothing, so you can simply omit it. So the second equation reduces to (A'B+A'CD)'.

Both of these results are easily realized using NAND gates, since a NAND is simply an OR using negative logic at the input.

#### Dennisc

##### New Member
Thanks for the help. I have about 20 more problems like this to do before Wednesday night. I am trying to figure these two out and it looks like the first problem ends up A'+AC and problem two A'B+A'CD. It looks like problem two should end up with a line above it from the inverter on the end of it. If these are the two final answers then do I go from here and try to draw out the problem? Is this the place where I should DeMorgan the problems? Is this where I need ot get rid of the +'s to switch to a NAND gate? Sorry to ask so many questions, I am just having a hard time understanding this logic stuff. Once I get these first problems solved I am sure I will understand how to do the rest.
Thanks Dennis

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##### Well-Known Member
Dennisc said:
Thanks for the help. I have about 20 more problems like this to do before Wednesday night. I am trying to figure these two out and it looks like the first problem ends up A'+AC and problem two A'B+A'CD. It looks like problem two should end up with a line above it from the inverter on the end of it. If these are the two final answers then do I go from here and try to draw out the problem? Is this the place where I should DeMorgan the problems? Is this where I need ot get rid of the +'s to switch to a NAND gate? Sorry to ask so many questions, I am just having a hard time understanding this logic stuff. Once I get these first problems solved I am sure I will understand how to do the rest.
Thanks Dennis
Yes, once you do that reduction, it is time to Demorgan to all AND or NAND. I would normally just start drawing gates at this point.

#### Dennisc

##### New Member
Does this by any chance look right. Probably not but this is my first one.
Thanks Dennis

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#### Dennisc

##### New Member
I attached again the same two circuits, I tried to DeMorgan them so I could write them with NOR gates only. Do these two circuits look like they're ready to draw or are there errors in them.

Thanks Dennis

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