| 摘要 |
PROBLEM TO BE SOLVED: To attenuate gain to the vicinity of 0 in desired frequency, without adjusting the on-resistor RSk of a switch, depending on k, even when resistance value Rk of a variable resistor is not negligible with respect to 'R1 +...+Rk'. SOLUTION: This variable RC filter consists of a plurality of resistors R1 -Rn , connected in series and a capacitor with its one end connected to these resistors and changes the connection of these resistors, has a plurality of first switches S1 -Sn , which break the circuit between several adjacent resistors among the plural resistors, a plurality of second switches SF1-SFn, which break the circuit between one end on input side of the switches S1 -Sn and a capacitor, a plurality of third switches SB1-SBn, which break the circuit between one end on output side of the switches S1 -Sn and the capacitor, and a band control circuit 14, which outputs a control signal with variable polarity for controlling the break of the first, second, and third switches, whose frequency bands are controlled by the signals from a control terminal 4.
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