| 摘要 |
PURPOSE:To absorb automatically the variance in a filter characteristic caused due to a capacitance value and a resistance value in an IC by making always the time constant constant and making an impressed voltage across the junction capacitance in the IC equal to each other. CONSTITUTION:Against the variance in the filter characteristic shown in curves A, B caused due to variance of a resistor Ra in the IC and a junction capacitor Ca in the IC, the characteristic is controlled to the filter characteristic C coincident with an output D of a generation circuit 6 at a frequency fin of a reference signal source 5 and the product (time constant) between the resistance Ra and the capacitane Ca is made always constant. Further, the specific accuracy of resistors Rb1-Rb4 in the IC, junction capacitors Cb1-Cb4 in the IC, a resistor Ra in the IC and a junction capacitor Ca in the IC constituting a high pass filter 21 being a desired integrated filter is selected sufficiently, and the voltage applied across the junction capacitors Ca, Cb1-Cb4 in the IC is kept equal, the capacitance of the junction capacitors in the IC is changed similarly and the variance of the filter characteristic in the high pass filter 21 is absorbed automatically.
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