| 摘要 |
PURPOSE:To obtain a low-pass active filter whose dynamic range is expanded by connecting a resistor between an input and an output and inserting a gyrator between one end of the resistor and ground. CONSTITUTION:An impedance converting circuit 10 consists of an Antonio type gyrator and the transfer function T(S) is expressed as T(S)=r/[(r+R)+Rr/Zin], where Zin is an impedance viewed from an IN terminal. The transfer function T(S) is formed as that of a low-pass filter based on the characteristic of the gyrator circuit by changing the connection of circuit elements of the impedance converting circuit 10 so as to change the impedance Zin. The 2nd order low-pass filter is constituted by forming, e.g., as R1=0 and C3=0. The DC gain in this case is expressed as K=r/R+r, which is less than the unity, then the dynamic range is expanded. |
