Patent ID: 7808414

Claim:
An A/D conversion circuit comprising: a continuous-time filter that performs a filtering process on an input signal; a switched-capacitor filter that is provided in a subsequent stage of the continuous-time filter and performs a filtering process utilizing the continuous-time filter as a prefilter, a cut-off frequency of the switched-capacitor filter being variably set corresponding to a frequency band of the input signal; an A/D converter that is provided in a subsequent stage of the switched-capacitor filter and performs an A/D conversion operation utilizing the continuous-time filter and the switched-capacitor filter as prefilters; and a digital filter that is provided in a subsequent stage of the A/D converter and performs a digital filtering process utilizing the continuous-time filter and the switched-capacitor filter as prefilters, a cut-off frequency of the digital filter being variably set corresponding to the frequency band of the input signal.