Q 12-14-152JEE MainJEE Main 2021 (26 Feb, Shift 2)Medium
Draw the output signal $Y$ in the given combination of gates.
Answer: (A) see figure
The first gate is a NAND with both inputs tied to $A$, so its output is $\bar{A}$. This goes into an OR gate with $B$, followed by a NOT gate:
$$Y = \overline{\bar{A} + B} = A\cdot\bar{B}$$
So $Y = 1$ only when $A = 1$ and $B = 0$.
From the waveforms: $0$–$1$ s ($A=1, B=0$): $Y = 1$; $1$–$2$ s ($B=1$): $Y = 0$; $2$–$3$ s ($A=0$): $Y = 0$; $3$–$4$ s ($B=1$): $Y = 0$; $4$–$5$ s ($A=1, B=0$): $Y = 1$.
The output is high from $0$ to $1$ s and from $4$ to $5$ s.
Solution by Sreeraj P, M.Sc Physics