Patent ID: 7466192

Claim:
A low-pass filter attenuating a high frequency component of an input signal and outputting a low frequency component of the input signal as an output signal, comprising: a differential operation circuit subtracting the output signal from the input signal and outputting a differential signal; a voltage-current conversion circuit converting a voltage of the differential signal outputted from the differential operation circuit into a current; and a capacitance accumulating charges in a current received from the voltage-current conversion circuit to generate the output signal, wherein the voltage-current conversion circuit including: a first operational amplifier having a noninverting input terminal connected to an input terminal of the voltage-current conversion circuit and an inverting input terminal receiving a feedback voltage; a first resistor connected between an output terminal of the voltage-current conversion circuit and an output terminal of the first operational amplifier; and a feedback unit for generating the feedback voltage in accordance with a voltage applied to the first resistor.