On the realization of switched-capacitor integrators for sigma-delta modulators

University essay from Linköpings universitet/Institutionen för systemteknik; Linköpings universitet/Institutionen för systemteknik


The sigma-delta techniques for analog-to-digital conversion have for long been utilized when high precision is needed. Despite the fact that these have been realized by a numerous of different structures, the theory of how to construct a sigma-delta ADC is not very extensive.

This thesis will assume that an SFG description of the CRFB sigma-delta modulator has been designed and presents a structured method to obtain a circuit realization of the integrators in a specific modulator.

The first activity is to scale the inputs to each integrator in order to make sure that the produced outputs of each integrator is within the output-range of the OTA which is used. The next thing that is presented is an algorithmic way of descending from the SFG design of the modulator down to a switched-capacitor implementation of the system.

To be able to continue with the circuit realization, one needs to do a rigorous noise analysis of the modulator, which gives the sizes of the different capacitors in the SC-circuits. The last topic of this thesis is a method to obtain the specifications of the OTA in each integrator.

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