How do you construct a 3 ip nand gate using only 2 ip nand gates?

Answer 1

To produce a 3-input OR gate when only 2-input OR gates are available: Use 3 OR gates Inputs to Gate A are input 1 and input 2 Input to Gate B is input 3 (if 2 inputs are necessary, include input 3 and FALSE) Inputs to Gate C are outputs from Gate 1 and Gate 2 === If input 1 OR 2 is TRUE, output of Gate A will be TRUE. If input 3 is TRUE, output of Gate B will be TRUE. If output of Gate A OR Gate B is TRUE, output from Gate C will be TRUE. That is if one ore more of Inputs 1, 2 or 3 is TRUE, the result will be TRUE. Otherwise, output of Gate C will be FALSE.

Answer 2

you can take 2 input or gate first 2inputs and output of that gate should be given as the input for next OR gate with 3rd input

Above solution will not work if all 3 inputs are True. I believe the question requires a configuration of XOR gates that will produce a True result if EXACTLY one out of three inputs is True.

Specifically, if Inputs A and B are both True, the first XOR Gate output will be False. If Input C is also True, the second XOR Gate output will be True, yielding an overall TRUE result. This is not the desired result.

I don't know the correct answer, but I'm pretty sure the first answer is not complete.

Truth table for 3 input XOR gate

INPUTS OUTPUTS

ABC X

000 0

001 1

010 1

011 0

100 1

101 0

110 0

111 1

From the table we can use 2 XOR gates to get 3 inputs XOR with the same result.

1st XOR Gate

AB X

00 0

00 0

01 1

01 1

10 1

10 1

11 0

11 0

2nd XOR Gate

XC Y

00 0

01 1

10 1

11 0

10 1

11 0

00 0

01 1

I was also confuse for when 3 inputs are 111, but I'm now sure from few references saying that 111 input will produce an output of 1.