Abstract: A separation circuit part is used to separate an amplified signal path from a feedback signal path. An amplifier circuit part comprises a resistor-loaded common-source FET, a level adjustment diode and a source-follower circuit. The separation circuit part comprises a source-follower circuit, an output part of which is connected to a feedback circuit part comprising a resistor, thereby forming a feedback signal path to an input terminal of the amplifier circuit part. The signal separation circuit is used to separate the amplified signal path from the feedback signal path, thereby reducing the loads of the signal paths. In this way, the loads of the amplified signal and feedback signal paths are reduced.