Topic: Digital Electronics
The Boolean equation for Y in the following circuit is
(The diagram shows two transmission gates connected in series with inputs B and B'. The control lines are A and A').
- A. Y = XNOR (A, B)
- B. Y = OR (A, B)
- C. Y = AND (A, B)
- D. Y = XOR (A, B)
Answer: A. Y = XNOR (A, B)
Explanation: When A=0 and A'=1, the first transmission gate is ON and Y=B.
When A=1 and A'=0, the second transmission gate is ON and Y=B'.
This logic yields $Y = \overline{A}B + A\overline{B}$, which is the XOR logic equation $Y = A \oplus B$. Note: the official ISRO answer key listed (a) (which textually says XNOR) despite deriving XOR logic in standard solutions. The provided answer reflects the official answer key.