| 摘要 |
PURPOSE:To eliminate the effect of an input voltage by providing a MOS transistor(TR) and a capacitive element and varying its gate voltage in response to the AC component of an input voltage in varying the gate voltage to make the filter characteristic adjustable. CONSTITUTION:A voltage equal to the AC component Vin(AC) of an input voltage Vin is given to a gate voltage Vc of MOS TRs M1, M2 so as to cancel the fluctuation of gate-source voltages VGS1, VGS2 of the TRs M1, M2. That is, the relation of voltages is selected to be Vc=Vc(DC)+Vin(AC), then for example, the gate-source voltage VGS1 of the TR M1 is expressed as VGS1=Vin-Vc=[Vin(AC)+-Vin(DC)]-[Vc(DC)+-Vin(AC)]=-Vin(DC)-Vc(DC) and said voltage remains constant. Through the constitution as above, the impedance is made so as not to be affected by the fluctuation of an input voltage and to reduce distortion.
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