NIELIT 2017 July Scientist B (CS) - Section B: 21

Question

The combinational circuit given below is implemented with two NAND gates. To which of the following individual gates is its equivalent?

• A. NOT
• B. OR
• C. AND
• D. XOR

Comments

Option C

Answer 1

It is AND gate implementation using NAND gate.  To design $2$ input AND gate we required $2$ NAND gate.

Here the output of the first NAND gate is given as input for $2^{nd}$ NAND gate. We can write an equivalent expression for it.

$f=\overline{\left[\overline{(a.b)}.\overline{(a.b)}\right ]}$

$f=\overline{\overline{(a.b)}}+\overline{\overline{(a.b)}}$

$f=(a.b)+(a.b)$
$f=(a.b)$

$f$ is AND gate whose input is $a,b$

So Option $(C)$ is correct.