Patent ID: 7675446

Claim:
A filter, comprising: an integrator, for integrating an input signal to output an integral signal; a signal attenuator, coupled to the integrator, for attenuating the integral signal to output an attenuation signal; and a switched-capacitor, coupled between the signal attenuator and the integrator, for feeding back the attenuation signal to the integrator; wherein an amplitude of the attenuation signal is smaller than an amplitude of the integral signal, and wherein the integrator comprises: an operational amplifier, having an input end and an output end; an integrating capacitor, having a first end and a second end, the first end of the integrating capacitor is coupled to the input end of the operational amplifier and the second end of the integrating capacitor is coupled to the output end of the operational amplifier; a switching circuit, having a first end and a second end, the second end of the switching circuit is coupled to the first end of the integrating capacitor and the input end of the operational amplifier; and a second switched-capacitor, having a first end and a second end, the second end of the second switched-capacitor is coupled to the first end of the switching circuit and the first end of the second switched-capacitor is coupled to the input signal, and the switched-capacitor is coupled to the second end of the second switched-capacitor and the first end of the switching circuit.