In an attempt to study the behavior of dynamic circuits in the presence of deep submicron noise when operating at a low supply voltage, this paper presents noise tolerant design and analysis for an enhanced dynamic full adder cell based on the NORA-CMOS logic style. The noise tolerance capability is achieved by applying the twin-transistor technique on both the p and the n parts of the circuit. A prototype is constructed for both the standard and the designed noise tolerant circuits using 0.18 /spl mu/m CMOS technology and simulated using HSPICE at supply voltage ranges from 0.9 V to 2.7 V. Noise immunity curves are developed and used to calculate the average noise threshold energy which shows a 2.5 times improvement when compared with the conventional design. The noise enhancement comes at the expense of 2.1 times extra power consumption.