NEETPhysicsSemiconductors
In a logic circuit, two inputs A and B are fed into a NOR gate. The output of this NOR gate is then connected to both the inputs of a NAND gate to produce the final output Y . Which of the following correctly describes the sequence of output states of Y for the input combinations (A, B) = (0, 0), (0, 1), (1, 0), and (1, 1) respectively?
Options
- A1, 0, 0, 0
- B0, 1, 1, 1
- C0, 0, 0, 1
- D1, 1, 1, 0
Correct answer
B. 0, 1, 1, 1
Step-by-step solution
The first gate is a NOR gate, so its output is Y₁ = A+B . This output Y₁ is fed into both inputs of a NAND gate. A NAND gate with tied inputs acts as a NOT gate. Therefore, the final output Y is given by: Y = Y₁ Y₁ = Y₁ Substituting Y₁ into the equation: Y = A+B = A+B This is the Boolean expression for an OR gate. The truth table for an OR gate gives an output of 0 only when both inputs are 0 , and 1 otherwise. Thus, for the input sequence (0, 0), (0, 1), (1, 0), (1, 1) , the output sequence is 0, 1, 1, 1 . Answer: