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JEE Main 2014 (19 Apr, Shift 1) · Logic Gates

Logic Gates question from JEE Main 2014 (19 Apr, Shift 1)

Q161JEE Main 2014 · 19 APR · SHIFT 1Medium

Logic Gates

Figure

Given: A and B are input terminals.

Logic 1 = > 5 V

Logic 0 = < 1 V

Which logic gate operation, the following circuit does?

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Answer: (a)

  1. Diode cathodes face the inputs; the output is held high by VccV_{cc} unless a diode conducts.
  2. If A or B is at logic 0 (below 1 V), that diode is forward biased and pulls VoutV_{out} low.
  3. Only with both A and B at logic 1 do both diodes stay off, so VoutV_{out} is high.
  4. Output 1 only when both inputs are 1. So the answer is (a) AND gate.
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