Patent ID: 8466820

Claim:
An oversampling A/D converter configured to perform digital conversion of an input signal, the oversampling A/D converter comprising: a first filter including a first resistive element configured to receive the input signal at a first end, a first capacitive element coupled to a second end of the first resistive element at a first end, and coupled to a common node at a second end, a second resistive element coupled to the first end of the first capacitive element at a first end, an operational amplifier coupled to a second end of the second resistive element at an inverting input terminal, and coupled to the common node at a non-inverting input terminal, and a second capacitive element coupled between an output terminal and the inverting input terminal of the operational amplifier, the first filter configured to output a signal from the output terminal of the operational amplifier; a second filter configured to receive an output of the first filter; a third filter including a third resistive element configured to receive the input signal at a first end, a third capacitive element coupled to a second end of the third resistive element at a first end, and coupled to the common node at a second end, and a fourth resistive element coupled to an output terminal of the second filter at a first end, and coupled to the first end of the third capacitive element at a second end, the third filter configured to output a signal from the first end of the third capacitive element; a quantizer configured to receive an output of the third filter and generate a digital signal; and a D/A converter configured to convert the digital signal to an analog current signal, and input the current signal to the inverting input terminal of the operational amplifier.