The minimum number of 2-input NAND gates required to realise sum and carry of a half adder

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Answer (Detailed Solution Below)

Option 1 : 4
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Sum expression of a half adder is given by:

Sum = A XOR B = \(\bar A\;B + A\;\bar B\)

The implementation of half adder circuit is shown below:

606209c9bcf7ddc24a2f62ec 16354956368901

We can conclude that to generate the sum bit, we only need 4 NAND gates.

26 June 1

Logic Gates

Min. number of NOR Gate

Min. number of NAND Gate

NOT

1

1

AND

3

2

OR

2

3

EX-OR

5

4

EXNOR

4

5

NAND

4

1

NOR

1

4

Half-Adder

5

5

Half-Subtractor

5

5

Full-Adder

9

9

Full-Subtractor

9

9

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