Why Sigma-Delta modulator?

[Boki]

Why Sigma-Delta modulator?

 

[CFoley1064]

Why Sigma-Delta modulator?

Analog Devices has a fairly lengthy (1.7 MB) resource which will answer your
question --

http://www.analog.com/UploadedFiles/Application_Notes/42915257172450549236
80458171AN283.pdf

Sigma Delta ADCs and DACs -- Overview of Sigma-Delta Concepts: Oversampling,
Noise Shaping Using the Sigma-Delta Modulator, Digital Filtering and Decimation

Good luck.
Chris