Which gate combination is used to generate the sum and carry outputs in a full…
2024
Which gate combination is used to generate the sum and carry outputs in a full adder circuit?
- A.
XOR of inputs for sum; AND only for carry.
- B.
AND of inputs for sum; XOR, OR, and AND for carry.
- C.
XOR of inputs for sum; XOR, AND, and OR for carry.
- D.
OR of inputs for sum; XOR, AND, and OR for carry.
Attempted by 103 students.
Show answer & explanation
Correct answer: C
A full adder takes three 1-bit inputs: A, B, and carry-in Cᵢₙ. It produces a Sum output S and a Carry-out output Cₒᵤₜ.
Sum output:
S = A ⊕ B ⊕ Cᵢₙ
So the sum is generated using XOR logic.
Carry output in the common two-half-adder implementation:
Cₒᵤₜ = (A · B) + (Cᵢₙ · (A ⊕ B))
So the carry path uses XOR to form A ⊕ B, AND gates to form partial carry terms, and an OR gate to combine those terms.
Therefore, the correct option is: XOR of inputs for sum; XOR, AND, and OR for carry.