A fast binary adder with conditional carry generation

Jien Chung Lo, IEEE


This brief contribution presents a fast binary adder in static CMOS realization. While the carry derivation is similar to that in a conditional-sum adder, the proposed adder is also similar to that of a spanning tree carry lookahead adder in the sense that only selected carry bits are generated and the sum bits are produced by carry-select adders. In a 1.2 μm static CMOS realization, the proposed adder adds two 32-bit operands in 3.28 ns. This delay is measured from the assertion of the input to the arrival of the slowest sum bit. © 1997 IEEE.