Importance

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Abstract

The objective of this invention is to provide a type of addition circuit that can perform addition at a high speed without increasing power consumption, as well as a type of multiplication circuit and a type of multiplication/addition circuit having said addition circuit as the last step. It has a characteristic feature that the delay in a signal input from a Wallace tree to the addition circuit in the last step is maximum in the intermediate bit range, and it is smaller in the lower and upper bit ranges. In the lower bit range, addition is performed by means of 1-level carry increment adder 1 with a larger delay in carry propagation to the upper place. In the intermediate bit range, addition is performed by means of 2-level carry increment adder 1 having a carry propagation speed higher than that in said lower bit range. In the upper bit range, addition is performed by means of high-speed carry select adder 3. In this way, because addition is performed using addition schemes matched to the trend of delay in the signal input timing in the various bit ranges, it is possible to perform computing at high speed while the circuit scale and power consumption are reduced.

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First Claim