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GATE 2020 IN – Question 21

Digital Electronics · Number systems and combinational logic: Number systems, multiplexer and demultiplexer, truth tables, minimization of Boolean functions, IC families (ECL, TTL, CMOS), CMOS logic gates, arithmetic circuits · 1 mark · Multiple choice

Choose the Boolean expression represented by the shaded Venn regions in the figure.

Diagram for GATE 2020 IN question 21
  1. $(A+B)(\bar A+\bar B)$
  2. $(A+\bar B)(\bar A+B)$
  3. $(\bar A+B)(\bar A+\bar B)$
  4. $(\bar A+\bar B)(A+\bar B)$

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Show answer and explanation

Correct answer: (A) $(A+B)(\bar A+\bar B)$

Explanation

The shaded portions are A without B and B without A; their overlap is unshaded. Thus the function is exclusive OR, $A\bar B+\bar A B$. Expanding $(A+B)(\bar A+\bar B)$ gives exactly this expression because $A\bar A=B\bar B=0$. Hence A.

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