RIPPLE CARRY ADDER
The fundamental unit of a Ripple Carry Adder (RCA) given in Fig. 3.1 is a full adder which computes a sum bit and a carry bit.
Sum bit can be represented as
Si = (ai XOR bi) XOR ci (3.7)
Carry bit can be represented as
Carry = aibi + bici+ ciai (3.8)
An n-bit Ripple Carry Adder
The architecture signifies that it adds two operand bits to produce a sum bit and a carry bit, since in the worst case the carry can propagate from the least significant bit position to most significant bit position.
In this case one single bit full adder is adding three bits viz.( a0, b0, c0), where a’s and b’s are the input of these sections and c’s are representing the carry input values. The delay and power calculation of various length ripple carry adder (using 90nm standard CMOS technology)