| 摘要 |
PURPOSE:To prevent the deterioration in the S/N by connecting a variable resistive element whose resistance value is changed by a control signal between an inverting input and a non-inverting input of a differential amplifier. CONSTITUTION:When no control input is given, a resistance value of the variable resistive element 8 becomes infinite. In this case, an output voltage V0 of the differential amplifier 4 is applied directly to a terminal P of the variable resistive element 8. Thus, a voltage corresponding to a loss of resistors 30, 36 is applied to the variable resistive element 8. As a result, the distortion of the AC component is suppressed remarkably. That is, since an amplitude of an AC signal voltage given across the variable resistive element 8 when a high level input is given is remarkably decreased, the distortion of the AC amplitude waveform is reduced. |
