To implement the Boolean equation \( Y = A + B \) in a digital circuit, the most suitable logic gate is the OR gate. Here's why:

1. Understanding the Boolean Equation:

• The equation \( Y = A + B \) is a logical OR operation. This expression signifies that the output \( Y \) will be true (or '1') if either input \( A \) is true, or input \( B \) is true, or both are true.

2. Logic Gate Options:

• OR Gate: The OR gate is specifically designed to perform this exact operation. It outputs true if any one or more of its inputs are true.
• AND Gate: Performs a logical AND operation, outputting true only if all of its inputs are true. This gate cannot replace the OR operation.
• NAND Gate: This gate is a combination of an AND gate followed by a NOT gate. It outputs the inverse of an AND operation and is not suitable for directly implementing an OR operation without additional circuitry.
• NOT Gate: This gate inverts the input signal (i.e., if the input is true, it outputs false and vice versa). It cannot implement the OR operation by itself.

3. Conclusion:

• To achieve the function \( Y = A + B \), the most direct and appropriate choice is the OR gate.

Therefore, the correct answer is the OR gate.