The given circuit works as : [figure]
- NOR gate
- OR gate
- AND gate
- NAND gate
Answer
(4) NAND gate
Solution
All four gates in the circuit are NOR gates.
A NOR gate with both inputs joined acts as a NOT gate: A + A = A
Outputs of the first two gates are A and B.
Third gate (NOR): Y1 = A + B = A B (De Morgan's theorem)
Last gate (inputs joined, acts as NOT): Y = Y1 = A B
The circuit works as a NAND gate.
Answer: (4)