Lecture 20: Noise-shaping ADC: Deriving the Error-feedback structure; Intro to delta-sigma modulator

This lecture starts with an attempt to improve the resolution of an ADC by subtracting the quantization noise. Subtraction of this residue at the output side (in the digital domain) gives rise to pipelined ADCs which was extensively discussed in the earlier lectures. So as an alternative,  the residue is subtracted at the input side (in the analog domain).  Owing to the inherent delay in this residue estimation, it is observed that one cannot exactly cancel the residue but only predictively correct it. This naturally gives rise to the error-feedback (EF) noise-shaping. It is noted that noise-shaping has to be done in conjunction with oversampling to reap the benefits of improved resolution.
Modifying this EF structure, gives rise to the powerful delta-sigma modulator (1st order). It is noted that this is once again a negative feedback system employing an integrator to force the average error to zero. A general framework of obtaining higher-order noise-shaping is also introduced.


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Instructor: R. S. Ashwin Kumar ( https://home.iitk.ac.in/~ashwinrs )
MVLSI, EE, IIT Kanpur


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