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JEE Main 2021 (31 Aug, Shift 2) · Logic Gates

Logic Gates question from JEE Main 2021 (31 Aug, Shift 2)

Q136JEE Main 2021 · 31 AUG · SHIFT 2Medium

Logic Gates

If VA and VB are the input voltages (either 5V or 0V) and V0 is the output voltage then the two gates represented in the following circuit (A) and (B) are :-

Figure

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Answer: (b)

  1. Circuit (A): if either VAV_A or VBV_B is 5 V, that diode conducts and V0≈5V_0 \approx 5 V; only when both are 0 V is V0=0V_0 = 0. This is OR.
  2. Circuit (B): VB=5V_B = 5 V drives the npn transistor into saturation, so V0≈0V_0 \approx 0; VB=0V_B = 0 cuts it off, so V0=5V_0 = 5 V. This is NOT.
  3. So the answer is (b) OR and NOT Gate.
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