A comparative study on adders

In a digital circuit, the addition of certain number of bits is generic operation used in order to pare the complexity of the circuit and it operation. The selection of proper adder with requisite properties is more important for the efficient working of the circuit. Comparisons among different adders have been performed, which helps to reduce the laborious work. Adders that have been compared are all of 4 bit and have been synthesized using Xilinx synthesis tool and simulated using the Xilinx simulation tool. The outcomes of synthesis reports and simulation of the circuit helps in finding out the different properties. For paradigm, the area consumed or the number of slices taken up by the circuit and speed can be calculated. These properties make out the difference in the operation and performances of the adders. The adders that have been compared in this paper are Ripple Carry Adder, Carry Look Ahead Adder, Carry Save adder, Carry Skip Adder, Carry select adder, Modified Carry Select Adder and Kogge Stone Adder based on two basic aspects namely, number of slices i.e., area occupied and speed.