Question:medium

The output (Y) of logic circuit given below is 0 only when :
logic circuit

Updated On: Jan 13, 2026
  • A = 1, B = 0
  • A = 0, B = 0
  • A = 1, B = 1
  • A = 0, B = 1
Show Solution

The Correct Option is B

Solution and Explanation

To ascertain when the output \( Y \) of the provided logic circuit is 0, we examine its components and their operation with inputs \( A \) and \( B \).

Step 1: Logic Gate Identification
Circuit Analysis:
- An OR gate receives inputs \( A \) and \( B \).
- A second OR gate takes the output of the first OR gate and a constant input 1.
- An AND gate receives inputs \( A \) and \( B \); its output is fed into the final OR gate.

Step 2: Circuit Behavior Analysis
1. The first OR gate outputs 1 if \( A = 1 \) or \( B = 1 \). Its output is 0 only when \( A = 0 \) and \( B = 0 \).
2. The second OR gate has a fixed input of 1. As an OR gate outputs 1 if any input is 1, this gate will consistently output 1, irrespective of the first OR gate's output.
3. The AND gate outputs 1 only when both \( A = 1 \) and \( B = 1 \). In all other scenarios, it outputs 0.
4. The final OR gate determines \( Y \), receiving inputs from the AND gate and the second OR gate. Since the second OR gate always outputs 1, \( Y \) can only be 0 if the other input (from the AND gate) is also 0.

Step 3: Condition for \( Y = 0 \)
For \( Y \) to be 0, the input conditions must result in the AND gate outputting 0. This occurs when \( A = 0 \) and \( B = 0 \).

Therefore, the necessary condition is:

\[ A = 0, \, B = 0. \]
Consequently, option (2) is correct.

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