Question

In the given circuit, value of Y is

• A. Toggles between 0 and 1

Answer 1

Answer: (A)

Toggles between 0 and 1

Answer 2

1. Gate Analysis:

• In the first branch, the inverter gives NOT(1) = 0. The NAND gate with inputs 0 and 1 then gives NAND(0,1) = 1.
• In the second branch, the buffered 1 remains 1. That 1 and the output of a third NAND gate feed a second NAND.
• The third NAND has one input as 0 (fixed) and its other input from the second NAND. Since NAND(0, anything) = 1, its output is 1, so the second NAND finally gives NAND(1,1) = 0.

2. Conflict and Feedback:

Both these NAND outputs (one 1 and one 0) are tied to the common output Y. Such a contention with feedback, along with the inherent delays in the real gates, forces the circuit into a race condition. This causes Y to oscillate (toggle) between 0 and 1.