Patent ID: 7078948

Claim:
A low-pass filter, comprising: a first element block having a capacitive element; a second element block having a resistive element, the second element block being connected in series to the first element block; a first input terminal for receiving a first electric current, the first input terminal being provided at a side including the second element block; a second input terminal for receiving a second electric current, the second input terminal being connected to a connection point of the first element block and the second element block; and an operational amplifier having a normal phase input terminal, an inverted phase input terminal, and an output terminal, the first and second element blocks being provided between the inverted phase input terminal and the output terminal, the normal phase input terminal being supplied with a reference voltage, wherein the first input terminal is provided at a side including the inverted phase input terminal of the operational amplifier, the second electric current is an electric current whose direction is the same as that of the first electric current and whose magnitude is N times that of the first electric current (where N is a predetermined number), and a total voltage generated in the first and second element blocks is employed as an output signal.