Patent ID: 7948412
Filing Date: 2011-05-24
Classification: H03M

Abstract:
1. A delta-sigma modulator, comprising: an input terminal; a continuous-time loop filter for receiving a continuous-time signal from said input terminal; a quantizer for outputting a digital signal obtained by quantizing an output from said continuous-time loop filter in response to a clock; a switched-capacitor feedback DA converter for outputting an analog signal depending on a first reference voltage according to the digital signal output from said quantizer, and for feeding back the analog signal to said continuous-time loop filter, said switched-capacitor feedback DA converter having a capacitor and a resistor; and a reference-voltage generating circuit for generating said first reference voltage, said reference-voltage generating circuit including a replica circuit of said switched-capacitor feedback DA converter, a detecting circuit for detecting a signal output from said replica circuit, and a voltage generator for generating a reference voltage based on the signal detected by said detecting circuit, an output from said voltage generator being said first reference voltage and also being input into said replica circuit; wherein said switched-capacitor feedback DA converter attenuating the output signal to be fed back to said continuous-time loop filter according to a time constant determined by said capacitor and said resistor, and said first reference voltage being variable.