| 摘要 |
<p>A second operational amplifier (7) is arranged, as an interface circuit (6), between a first operational amplifier (5) outputting the control voltage (Vcd) of a dummy filter (2) and a main filter (1), and the reference voltage (Vr) of the second operational amplifier (7) is optimized such that the control voltage (Vcd) obtained by using the dummy filter (2) is converted through the interface circuit (6) into a control voltage (Vcm) most suitable for the main filter (1), thereby obtaining a control voltage (Vcm) most suitable for regulating the frequency characteristics of the main filter (1) to desired characteristics.</p> |
