Abstract: An oversampling converter includes first and second integrators for integrating a difference between an input terminal voltage and feedback voltages, first and second quantizers for quantizing outputs from the first and second integrators, respectively, first and second feedback paths for feeding back as the feedback voltages outputs from the first quantizer to the input sides of the first and second integrators, a differentiator arranged at an output side of the second quantizer, an adder for adding an output from the differentiator and the output from the first quantizer, and a circuit for supplying an output from the first integrator to an input terminal of the second integrator. Two or more quantization loops may be used. When the oversampling converter is used as an A/D converter, A/D converters are arranged in the first and second feedback paths.

Abstract: In a switched capacitor circuit, in order to eliminate leakage of a power supply noise component to a signal line through an input capacitance of an operation amplifier, (1) an operating current of at least a first, differential stage among stages of the operational amplifier is regulated by a current regulation bias circuit, and (2) a power supply noise component having the same phase as that of an input signal is applied to the gate of a transistor of a gain stage, thereby stabilizing the operating point. In order to eliminate leakage of the power supply noise component to the signal line through a parasitic capacitance of an analog switch, (3) a dummy switch is used to detect a signal corresponding to the leakage component of the power supply noise component to the signal line, and an inverted signal having the opposite phase to that of the signal corresponding to the leakage component is applied to a substrate of the analog switch, thereby cancelling the actual leakage component.