There are provided an operational amplifier (A1), a capacitor (C1) capable of transmitting an input signal to an inverting input terminal of the operational amplifier, and a feedback path (B11) disposed between an output terminal and the inverting input terminal in the operational amplifier, and a reference voltage is supplied to a non-inverting input terminal. There is provided an input/output stabilizing circuit (B13) for changing a threshold voltage of the operational amplifier, and adding a micro signal input to the inverting input terminal of the operational amplifier, thereby carrying out an input/output stabilizing control in response to a signal output from the operational amplifier. In response to the signal output from the operational amplifier, the threshold voltage of the operational amplifier is changed and the micro signal is added to the signal input to the inverting input terminal of the operational amplifiers so that the input/output stabilizing control is carried out. By the control, the influence of a noise is eliminated and an enhancement in a noise resistance of a receiver circuit is achieved.