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GATE 2014 EC (EC4) – Question 26

Digital Circuits · Combinatorial Circuits · 1 mark · Multiple choice

Find output Y of the CMOS circuit shown.

Diagram for GATE 2014 EC (EC4) question 26
  1. $\overline A+\overline B+C$
  2. $A+\overline B\,\overline C+A\overline C$
  3. $\overline A+B+\overline C$
  4. $ABC$

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Show answer and explanation

Correct answer: (A) $\overline A+\overline B+C$

Explanation

The pull-down path consists of three NMOS devices in series controlled by A,B,C̄. It conducts exactly when ABC̄=1, pulling the output low. The complementary parallel PMOS network pulls high otherwise. Hence **Y=(ABC̄)̄=Ā+B̄+C,A**.