Patent ID: 7898448

Claim:
A sigma-delta analog-to-digital converter comprising: an input switching device for switching between a first input signal and a second input signal; a digital-to-analog converter unit for outputting a first level of electric charge and a second level of electric charge; an integrator unit for integrating outputs from the input switching device and the digital-to-analog converter unit and holding integrated values; a comparator unit for comparing integrated values output from the integrator unit with a predetermined value; a digital-to-analog switching device for switching an output of the digital-to-analog converter unit according to an output of the comparator unit; and an arithmetic operation unit for performing computation on an output signal of the comparator unit, wherein the comparator unit latches an integrated value held in a first capacitor of the integrator unit at a start of a second period and outputs a value latched at the start of the second period, and latches an integrated value held in a second capacitor of the integrator unit at a start of a fourth period and outputs a value latched at the start of the fourth period, and the arithmetic operation unit includes a differential operation unit for computing a difference of at least two comparison signals output from the comparator unit.