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I have two input NAND and NOR gates, I have attached their inputs and they both give the same result as the NOT gate, that is the inverter. Now i want to make further changes at the input side, so that their result is equivalent. I have tried alot making changes in the input side, adding gates and inverters, but I am not getting the same output. Can anyone suggest something?enter image description here enter image description here

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  • \$\begingroup\$ What do you mean by "making further changes on the input side, so their result is equivalent" What kind of changes? Please show an example. \$\endgroup\$ – tcrosley Feb 8 '14 at 10:27
  • \$\begingroup\$ Useful search term : "de Morgan". \$\endgroup\$ – Brian Drummond Feb 8 '14 at 10:37
  • \$\begingroup\$ By further changes i mean, adding more gates or inverters, so that their out put is same. \$\endgroup\$ – Marium Malik Feb 8 '14 at 10:45
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To make the NAND gate act identically to the NOR gate you have to attach an inverter to each input of the NAND gate and an inverter to the output of the NAND gate.

To make the NOR gate act identically to the NAND gate you have to attach an inverter to each input of the NOR gate and an inverter to the output of the NOR gate.

In order to understand why this is the case you need to understand how a Truth Table works for logic gates. If you don't know how a Truth Table relates to logic gates and logic design, you need to learn this. Lots of on-line resources to do so.

Once you learn how to use a Truth Table to represent logic gate functionality, then you will appreciate DeMorgan's Law. DeMorgan's Law explains a basic illusion of logic gates. Many beginners are fooled by this illusion. DeMorgan will explain this illusion and allow you to think logically about digital logic gates. The illusion relates directly to your question and more generally to the effect of inverting inputs and outputs of logic gates.

Who is this guy DeMorgan? He was a French mathemetician that died about 200 years ago. Did he have Nor gates and Nand gates too? Not likely, since it is known that he did not have a DigiKey account.

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  • \$\begingroup\$ FiddyOhm's and Andy aka's answers both seem to explain what you want. Read them both carefully and you should learn something useful. \$\endgroup\$ – Russell McMahon Feb 8 '14 at 11:19
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I suspect you mean what can you do to the 2 inputs to get equivalence at the output. Well the short answer is you need also to put an invertor on the output. Thie is deMorgan's rule: -

enter image description here

Basically, if you invert the inputs and outputs of an AND gate you get an OR gate. Likewise if you do the same to an OR gate you get an AND gate (that should be obvious once you know one).

The same applies with NAND and NOR - invert all the lines on a NAND and you get a NOR and vice versa.

See also this on stackoverflow

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