An overview of sigma delta ADCs and DAC devices

Presents a review and intuitive introduction to oversampling DSP techniques and the theory and advantages of sigma delta (Σ-Δ) devices for digital to analog conversion (DAC) and analogue to digital conversion (ADC). The paper initially introduces conventional Nyquist sampling rate DSP, followed by an overview of decimation, interpolation, and a discussion of the advantages of using oversampling to reduce the anti-alias and reconstruction filter specifications. It is then discussed why oversampling can be used to increase the resolution of an N-bit signal to N+1 bits, by sampling at 4× the Nyquist rate to reduce the in-band ADC quantisation noise. Sigma-delta (Σ-Δ) noise shaping techniques are then introduced and a brief overview of some devices is presented. Finally the authors comment on a few of the active research areas related to Σ-Δ devices