The GATE Grind

GATE 2021 PH – Question 36

Electronics · Basics of digital logic circuits, combinational and sequential circuits, flip- flops, timers, counters, registers, A/D and D/A conversion. · 2 marks · Multiple choice

The combination of logic gates shown represents which operation?

Diagram for GATE 2021 PH question 36
  1. OR
  2. NAND
  3. AND
  4. NOR

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Show answer and explanation

Correct answer: (B) NAND

Explanation

Each input is first inverted and the two inverted signals enter an OR gate. Its output is $\overline A+\overline B$. By De Morgan’s law this equals $\overline{AB}$, the NAND operation. For example, only the input pair $(1,1)$ produces output 0; the other three pairs produce output 1. Select B.

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