Abstract: A multi-bit continuous-time sigma-delta analog-to-digital converter (ADC) has a differential input stage which receives an analog input signal current. A multi-bit feedback current digital-to-analog converter (IDAC) generates a multi-level feedback current depending on a digital feedback signal from a flash ADC. An integrator has a differential input that integrates the difference of the generated current by the multi-bit IDAC and the input signal current on a continuous-time basis. The input stage further comprises a first biasing current source and a second biasing current source which bias the input stage in a mid-scale condition. A first summing node connects to the first differential input line, a first differential input of the integrator and the first output branch. A second summing node connects to the second differential input line, a second differential input of the integrator and the second output branch.

Abstract: A sigma-delta digital-to-analog converter comprises a current digital-to-analog converter (IDAC) stage which generates a current depending on an input digital signal. An output current-to-voltage converter converts the generated signal to a voltage on a continuous-time basis. The amplifier used in the output current-to-voltage converter is chopper-stabilized. The converter can be single bit or multi-bit. The IDAC stage can be implemented with a pair of branches, a first branch comprising a first biasing current source and a second branch comprising a second biasing current source. The biasing current sources can be chopper-stabilized by connecting the bias current sources to the output current-to-voltage converter by a set of switches. The switches connect the biasing current sources to the output current-to-voltage converter in a first configuration and a second, reversed, configuration. This modulates flicker noise contributed by the bias current sources to the chopping frequency.