Q 12-14-114JEE MainJEE Main 2022 (25 Jul, Shift 1)Medium
In the circuit, the logical value of $A = 1$ or $B = 1$ when the potential at $A$ or $B$ is $5\ \text{V}$, and the logical value of $A = 0$ or $B = 0$ when the potential at $A$ or $B$ is $0\ \text{V}$. The truth table of the given circuit will be:
Answer: (A) $\begin{array}{ccc}A & B & Y\\ \hline 0 & 0 & 0\\ 1 & 0 & 0\\ 0 & 1 & 0\\ 1 & 1 & 1\end{array}$
Each diode has its anode at the output node (pulled up to $5\ \text{V}$ through $R$) and its cathode at the input.
If either input is at $0\ \text{V}$, that diode is forward biased and pulls $Y$ down to $0$. Only when both inputs are at $5\ \text{V}$ are both diodes off, and $Y = 5\ \text{V}$.
So $Y = 1$ only for $A = B = 1$: an AND gate, table (1).
Solution by Sreeraj P, M.Sc Physics