The GATE Grind

GATE 2019 EC – Question 24

Digital Circuits · Combinatorial Circuits · 1 mark · Multiple choice

In the circuit shown, what are the values of F for EN = 0 and EN = 1, respectively?

Diagram for GATE 2019 EC question 24
  1. 0 and D
  2. Hi-Z and D
  3. 0 and 1
  4. Hi-Z and $\bar D$

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Show answer and explanation

Correct answer: (B) Hi-Z and D

Explanation

With $EN=0$ the gating logic turns both the pull-up pMOS and the pull-down nMOS off, so the output floats (Hi-Z). With $EN=1$ exactly one of them turns on according to $D$, so $F=D$. This is a tri-state buffer.