These full adders perform the addition of two 4-bit binary numbers. The sum (∑) outputs are provided for each bit and the resultant carry (C4) is obtained from the fourth bit. These adders feature a full internal look ahead across all four bits. This provides the system designer with the partial look-ahead performance at the economy and reduced package count of a ripple-carry implementation. The adder logic, including the carry, is implemented in its true form meaning that the end-around carry can be accomplished without the need for logic or level inversion.