| 摘要 |
PURPOSE:To decrease the number of required capacitors and the total capacitance, by providing a voltage divider between an output of an amplifier and an input of a charging/discharging capacitor group, changing over a voltage divided output and giving it to the capacitor group and making the characteristics of a titled filter variable. CONSTITUTION:The output of the amplifier 53 is divided by a voltage divider consisting of resistors 100, 101, and the divided voltage is outputted to a terminal A after being switched by switches 64, 65. The terminal A is connected to capacitors 96-98 in the way of time division with time division switches 82-87, and the capacitors 96-98 are connected to a terminal B in the way of time division. That is, a triple filter is constituted. Further, the change of a voltage at the terminal A by use of the switches 64, 65 is to change the effective capacitance of the capacitors 96-98 equivalently, and it is equivalent to have two kinds of different capacitor groups. Thus, the type of the filter is changed over by only varying the voltage dividing ratio of the voltage divider without increasing the number of capacitors. |
