Understanding the Full Adder
A full adder is a digital circuit that performs the arithmetic sum of three binary digits: two significant bits and an incoming carry bit from a previous less significant stage. It is fundamental in binary addition operations.
Functionality of Full Adder
- Inputs: The full adder takes three inputs:
- A: First bit
- B: Second bit
- Cin: Carry input from a previous addition
- Outputs: It produces two outputs:
- Sum (S): The resultant sum bit
- Cout: The carry output to the next higher bit
Application in 3-Bit Addition
- 3-Bit Addition: The full adder is specifically designed to handle the addition of three bits, which makes it suitable for 3-bit binary addition.
- Cascading Full Adders: For adding larger bit numbers, you can cascade multiple full adders. For example, to add three 3-bit numbers, you would use three full adders. Each full adder takes in a pair of bits along with the carry from the previous adder.
Limitation on Options
- 2-Bit Addition: While capable of performing 2-bit addition, a full adder is not specifically designed for it and is not the most efficient choice.
- 4-Bit Addition: Similarly, while it can be used for 4-bit addition by cascading, it is not the primary function.
- Unlimited Bit Addition: Theoretically possible, but impractical without an extensive arrangement of multiple adders.
Conclusion
The correct answer is option 'B' because the full adder excels at performing 3-bit addition directly, while it can be adapted for larger bit sizes through cascading.