Question

Which of the following gates will have an output of 1?

• A. (a) and (b)
• B. (b) and (c)
• C. (c) and (d)
• D. (d) and (a)

Answer 1

The correct option is C (c) and (d)

Case (a) : NOR gate. The output of this gate is given as
$Y_a=\overline{A+B}=\overline{1+1}$
$=\overline{1}=0$

Case (b): NOR gate.
Output $Y_b=\overline{A+B}=\overline{0+1}$
$=\overline{1}=0$

Case (c) : NAND gate. The output of this gate is given as
$Y_c=\overline{A.B}=\overline{0.1}$
$=\overline{0}=1$

Case (d) : XNOR gate. The output of this gate is given as
$Y_d=A.B+\overline{A}.\overline{B}=0.0+\overline{0}.\overline{0}$
$=0+1=1$

Hence the gates of figures (c) and (d) give output 1.