A 32-bit carry lookahead adder design using complementary all-N-transistor logic

Abstract

A complementary all-N-transistor (CANT) comprising the ANT logic and a novel inverted ANT logic is proposed in this paper. The threshold voltage of the transistors in the ANT logicpsilas N-block is variable depending upon the operation of the entire logic block. In the evaluation phase, the bulk voltage of the transistors in the N-block is raised to VDD - Vthn such that the drain current therein is increased to enhance operation speed. In the pre-charge phase, the bulk voltage of those transistors in the N-block is reduced to its normal voltage level such that the subthreshold leakage current is dropped to reduce power consumption. By utilizing such a variable bulk voltage scheme in the CANT, a 32-bit CLA is designed to justify the low power and high speed performance. The power dissipation is 143 mW at 5.4 GHz clock rate given the worst PVT (SS, 1.08 V, 75degC) condition.