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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumData or graph

JEE Main 3 August 2021, Shift 1, Physics Q20

Question 20 of 90 in this shift, Physics question 20 of 30, Section A.

In the given figure, a logic circuit has the input waveforms `A' and `B'. The correct output waveform will be -

The figure, in words

Circuit: input A (dot) goes through a NOT gate (triangle with small circle at output) and input B (dot) goes through a NOT gate; both outputs feed the two inputs of an OR-shaped gate that has a small circle at its output, which goes to a small-circle terminal labelled Y (Output). Label 'Inputs' beside A and B. Below, waveforms on a grid of dashed vertical lines with t=0 marked at the first line (intervals counted from t=0). Input A: high before t=0, then low, high, low, high, low, high for successive intervals 1-6. Input B: high before t=0, low for intervals 1-2, high for intervals 3-4, low for intervals 5-6. Four options are each a square-wave graph on the same kind of grid.
  1. (1)[figure: output square-wave graph with dashed vertical grid lines and t=0 marked at the first dashed line; high before t=0, low from t=0 for 2 intervals, high for 1 interval, low for 2 intervals, high for 1 interval]
  2. (2)[figure: output square-wave graph with dashed vertical grid lines and t=0 marked at the first dashed line; high before t=0, low from t=0 for 3 intervals, high for 1 interval, low for 2 intervals]Official answer
  3. (3)[figure: output square-wave graph with dashed vertical grid lines and t=0 marked at the first dashed line; high before t=0, low from t=0 for 1 interval, high for 2 intervals, low for 1 interval, high for 2 intervals]
  4. (4)[figure: output square-wave graph with dashed vertical grid lines and t=0 marked at the first dashed line; low before t=0, high from t=0 for 2 intervals, low for 2 intervals, high for 1 interval, low for 1 interval]

Official answer

Option 2

NTA final key.

Chapter
Semiconductor Electronics: Materials, Devices and Simple Circuits
Topic
Logic Gates
Idea tested
Timing Diagrams and Waveform Analysis

Same idea in other shifts

Asked 7× in all
  1. 8 Apr 2026, Shift 2 · Q45The output YY for the given inputs AA and BB to the circuit is :MediumDiagram basedHas a figure
  2. 8 Apr 2023, Shift 1 · Q42For the logic circuit shown, the output waveform at Y is:MediumDiagram basedHas a figure
  3. 13 Apr 2023, Shift 1 · Q47For the following circuit and given inputs A and B, choose the correct option for output 'Y'HardDiagram basedHas a figure
  4. 27 Jul 2022, Shift 1 · Q49A 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:EasyDiagram basedHas a figure
  5. 27 Jun 2022, Shift 1 · Q49Identify the correct Logic Gate for the following output (Y) of two inputs A and B.MediumDiagram basedHas a figure
  6. 26 Feb 2021, Shift 2 · Q4Draw the output signal Y in the given combination of gates.MediumDiagram basedHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.