Question Details

The output (Y) of the given logic implementation is similar to the output of an/a _____ gate.


Options

A

NAND

B

OR

C

NOR

D

AND

Show Answer

Correct Answer :

Option C

NOR

NOR

Solution :

The correct answer is NOR.

Let's analyze the given logic gate circuit step-by-step to find the expression for the final output Y:

1. Identify the logic gates and their inputs:
- The top gate is a NOR gate with inputs A and B.
- The bottom gate is a NAND gate with inputs B and A.
- The output of both gates are connected as inputs to the final AND gate on the right, which produces the output Y.

2. Determine the intermediate outputs:
- The output of the top NOR gate is:

Y1=A+B¯

- The output of the bottom NAND gate is:

Y2=AB¯

3. Determine the final output expression:
Since the final gate is an AND gate, its output Y is the logical conjunction of the two intermediate outputs:

Y=Y1Y2

Substituting the intermediate outputs:

Y=(A+B¯)(AB¯)

4. Simplify the expression using Boolean algebra:
By De Morgan's laws:

A+B¯=A¯B¯

And:

AB¯=A¯+B¯

Substitute these expressions back into the equation for Y:

Y=(A¯B¯)(A¯+B¯)

Apply the distributive law:

Y=(A¯B¯A¯)+(A¯B¯B¯)

Since A¯A¯=A¯ and B¯B¯=B¯:

Y=(A¯B¯)+(A¯B¯)

Applying the idempotent law (X+X=X):

Y=A¯B¯

Applying De Morgan's Law once more:

Y=A+B¯

The resulting expression Y=A+B¯ is the boolean expression for a standard NOR gate.

5. Verification via Truth Table:

A B NOR Output: Y1=A+B¯ NAND Output: Y2=AB¯ Final Output: Y=Y1Y2
0 0 1 1 1
0 1 0 1 0
1 0 0 1 0
1 1 0 0 0

The final column values for Y correspond exactly to the truth table of a NOR gate.

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