AMPLIFIER CIRCUIT AND SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE

PROBLEM TO BE SOLVED: To provide an amplifier circuit and semiconductor integrated circuit device, wherein the cutoff frequency of a low-pass filter is easily and accurately set, and circuit scale is reduced. SOLUTION: The amplifier circuit includes a feedback circuit 12 which inverts and inputs an output signal of a differential amplifier circuit 10 to the differential amplifier circuit. The feedback circuit 12 includes a low-pass filter 20 including: an A/D converter 30 for converting the output signal into a digital signal; a digital signal processing section 40 for performing digital signal processing on the digital signal outputted from the A/D converter, based on a multiplication value multiplying the digital signal by a predetermined coefficient (k); and a D/A converter 50 for converting a signal outputted from the digital signal processing section into an analog signal. At the same time, a signal outputted from the low-pass filter 20 is inverted and inputted to the differential amplifier circuit 10. The cutoff frequency of the low-pass filter 20 is then set by digital signal processing performed in the digital signal processing section 40. COPYRIGHT: (C)2008,JPO&INPIT