Ripple carry adder is a combinational logic circuit used for the purpose of adding two n-bit binary numbers. It is also known as n-bit parallel adder. It is constructed by cascading n full adders in series. The carry out of the first stage is fed to the carry in of the next stage. n-bit ripple carry adder requires N full adders.
Block Diagram:
Truth Table:
Following is the final implementation of a 4-bit Ripple Carry Adder in the Cadence® design environment. Four 4-bit full adders are cascaded to obtain 4-bit ripple carry adder. (a3,a2,a1,a0) & (b3,b2,b1,b0) are two 4-bit numbers that are to be added and (s3,s2,s1,s0) is the output obtained. Cout is the final carry.
Final Schematic of 4-bit Ripple Carry Adder:
(a) When inputs are A(0001) & B(0011)
(b) When inputs are A(0011) & B(0011)
(c) When inputs are A(0111) & B(0111)
(d) When inputs are A(1111) & B(0111)
