A fundamental building block in digital arithmetic circuits that computes the sum of two binary digits along with a carry-in bit from a previous less significant stage. It produces two outputs: the sum bit and the carry-out bit. By cascading multiple full adders together, engineers create ripple-carry adders capable of summing multi-bit binary numbers in microprocessors and DSPs.
The critical path delay in the ALU is mostly determined by how fast the carry bit propagates through the 32-bit full adder chain.
Do not mix it up with
- Half adder: A half adder only adds two bits and has no input for a carry bit from a previous stage.
Related terms
Half adder
A digital logic circuit that adds two single-bit binary numbers and produces a sum and a carry output.
Arithmetic logic unit
The digital circuit block inside a processor that performs integer math and bitwise operations.
Combinational logic
A type of digital logic where outputs are determined entirely by the present combination of inputs.
XOR gate
A digital logic gate that outputs a high signal only when its two inputs are at different logic levels.