The Magic of Delta‐Sigma Modulation

This chapter discusses the need for oversampling data converters and presents a brief overview of the origins of delta-sigma modulators. Since the physical world nevertheless remains stubbornly analog, data converters are needed to interface with the digital signal processing (DSP) core. Data converters, including analog-to-digital converters (ADCs) and digital to analog converters (DACs), can be classified into Nyquist-rate and oversampled converters. In the former category, there exists a one-to-one correspondence between the input and output samples. Oversampling data converters are able to achieve over 20 ENOB resolutions at reasonably high conversion speeds by relying on a trade-off. They use sampling rates much higher than the Nyquist rate, typically higher by a factor between 8 and 512, and generate each output utilizing numerous preceding input values. The implementation of oversampling converters requires a considerable amount of digital circuitry, in addition to some analog stages, with both requiring to be operated faster than the Nyquist rate.