PURPOSE: To cope with various standards by providing a feedback terminal amplifier in which a polarity of an input terminal is converted depending on a set system standard while applying an output of a low pass filter to one side of an input terminal and applying an input to the other side of the input terminal.

CONSTITUTION: This circuit is composed of a low pass filter 303 composed of a resistor 4 and a capacitor C1 and three OP amplifiers. In this case, an input Vi is coupled to a positive side input of an output terminal amplifier 300 and an input terminal amplifier 301 and a negative side input of a feedback terminal amplifier 302, an output of the amplifier 301 is coupled to an input of the low pass filter 303, an output of the low pass filter 303 is coupled to a negative side of the amplifier 300 and a positive side of the amplifier 302, an output of the amplifier 302 is coupled to a negative side of the amplifier 301, an output V0 of the amplifier 300 is the final output. Thus, as this circuit is composed of circuits which can obtain a general characteristic, any standard can be satisfied.