Question

For which one of the following input combinations, the given logic circuit gives the output $Y=1$ ?

• A. A = 0 ; B = 0 ; C = 0
• B. A = 0 ; B = 1 ; C = 1
• C. A = 0 ; B = 1 ; C = 0
• D. A = 1 ; B = 1 ; C = 1
• E. A = 1 ; B = 0 ; C = 1

Answer 1

Answer: (B)

The logic circuit is

The output,
$Y=\overline{\overline{\bar{A}}\cdot B}+\overline{\bar{C}}=\overline{\overline{\bar{A}}\cdot \bar{B}\cdot \bar{C}}=\bar{A}\cdot B\cdot C$
$[\overline{A+B}=\bar{A}\cdot \bar{B}$, Demorgan's law]
when $A=0,B=1,C=1$, then $Y=1[\because \bar{A}=1]$