Patent ID: 7148829

Claim:
A delta-sigma modulation circuit with a gain control function, the circuit comprising: a variable gain amplifier; a gain-variable delta-sigma modulator; and a control unit that controls the gains of the variable gain amplifier and the delta-sigma modulator, wherein: the delta-sigma modulator is composed of a cascaded delta-sigma modulator, the cascaded delta-sigma modulator includes: a delta-sigma modulation type quantization loop of a first stage having a first integration circuit that inputs an input signal and a first feedback reference level; a first quantizer that quantizes an output from the first integration circuit; and a first converter that generates the first feedback reference level based on an output from the first quantizer; at least one delta-sigma modulation type quantization loops of second and subsequent stages, the loop being cascade connected to the delta-sigma modulation type quantization loop of the first stage, and having a second integration circuit that inputs a quantization loop-to-quantization loop signal and a second feedback reference level, the quantization loop-to-quantization loop signal being composed of a signal outputted from a given location in a delta-sigma modulation type quantization loop of a preceding stage; a second quantizer that quantizes an output from the second integration circuit; and a second converter that generates the second feedback reference level based on an output from the second quantizer; and a noise removing circuit having a delayer that delays an output from each of the delta-sigma modulation type quantization loops of the first stage and the second and subsequent stages; and a differentiator that differentiates an output from a delta-sigma modulation type quantization loop of a subsequent stage, the noise removing circuit adding the delayed outputs and the differentiated output, and outputting a value of the added outputs, and the control unit gain controls the noise removing circuit as well as the delta-sigma modulator.