with ever growing technology scaling, low power operation has become a necessity in VLSI design. Sigma Delta ADC consists major portions of the modern VLSI designs, thus efforts are being made to design low power ,small area sigma delta ADCs using different topologies and methodologies. This paper discusses various existing Sigma Delta modulator designs and topologies, consisting of different number stages and optimizations from one another. This paper focuses on the study of these designs and

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... heir comparison on the basis of parameters like power dissipation, structure order, bandwidth, OSR, FOM etc. All the designs studies are application and technology specific but the output bit patterns are similar for similar inputs with variations in rate of output. The simulation environment for the structures was chosen to be PSPICE A/D 16.6 and Sigma Delta Toolbox of MATLAB R2014a.