VLSI design of a 1.0 GHz 0.6-/spl mu/m 8-bit CLA using PLA-styled all-N-transistor logic

A high speed 8-bit carry-lookahead adder (CLA) using two-phase clocking dynamic CMOS logic with modified non-inverting all-N-transistor (ANT) blocks which are arranged in a PLA design style is presented in this paper. The pull-up charging and pull-down discharging of the transistor arrays of the PLA are accelerated by inserting two feedback MOS transistors between the evaluation NMOS blocks and the outputs. Detailed simulation results reveal appropriate L/W guidelines for the all-N-transistor (ANT) block design. The analysis of the area (transistor count) tradeoff is also provided in this work. The operating clock frequency is 1.0 GHz while the output of the addition of two 8-bit binary numbers is done in 2 cycles. The proposed design methodology is proved to be also suitable for the long adders, e.g., 64-b adders, while the correct output will be ready in 4 cycles if the 64-b adder is composed of hierarchical nine 8-b CLAs.