JEE Main 2022 · 27 July · morning · Single correct · +4 / −1
A logic gate circuit has two inputs A and B and output Y. The voltage waveforms of A, B and Y are shown below.
The logic gate circuit is :
- (a) AND gate
- (b) OR gate
- (c) NOR gate
- (d) NAND gate
Answer and solution
Answer (a) AND gate
Solution
Physics sir · 4 steps
Slice the time axis wherever any signal switches, then read A, B and Y in each slice as a truth table.
- Cut into intervals. Draw a vertical line at every edge where any of A, B or Y changes. That gives 7 equal intervals. In each one, write high as 1 and low as 0.
- Read the waveforms. Interval by interval, A reads 0, 1, 0, 1, 0, 1, 0 and B reads 0, 1, 1, 0, 0, 1, 0. The output Y reads 0, 1, 0, 0, 0, 1, 0. Every combination of A and B appears at least once.
A B Y from graph AND: A · B OR: A + B 0 0 0 0 0 0 1 0 0 1 1 0 0 0 1 1 1 1 1 1 - Rule out the rest. Y is 0 when only one input is high, so it is not OR. Y is 0 when both inputs are 0, so it is not NOR or NAND, which both give 1 there.
- So. Y is high only when A and B are both high, which is the truth table of an AND gate, option (a).
The idea to keep. For any waveform question, turn the graph into a truth table first. Then check the 0,0 row and one mixed row: those two alone separate AND, OR, NAND and NOR.
Answer from the NTA final answer key. Solution by PrepWiser.