A low power and reduced area carry select adder

A carry select adder (CSA) can be implemented by using a single adder block and an add-one circuit instead of using dual adder blocks. The add-one circuit is based on "first" zero detection logic and a few multiplexers. In the modified CSA, one of the n-bit adder blocks is replaced by an add-one circuit consisting of fewer transistors. This scheme considerably reduces the power and area, with negligible speed penalty. For 8-bit length, n=8, this modified CSA requires 38% fewer transistors and consumes only 73% of the power, compared to the conventional design, using a 0.5 /spl mu/m CMOS technology.