| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter circuit whose input voltage frequency gain is hardly changed by a frequency by a method, wherein a parallel circuit consisting of a low-pass filter and a band-pass filter which are connected in parallel to each other is provided in the filter circuit. SOLUTION: A parallel circuit 3, consisting of a low-pass filter 1 and a band-pass filter 2 which are connected in parallel to each other, is provided in a filter circuit, and an attenuation circuit 4 is connected to the input part of the band-pass filter 2 of the parallel circuit 3. If the frequency of a voltage inputted to the filter circuit is larger than 60Hz which is a reference frequency, the voltage is outputted with an advanced phase and, if the frequency of the input voltage is smaller than 60Hz which is a reference frequency, the voltage is outputted with a delayed phase. With this constitution, even if the frequency of the input voltage is around the reference frequency, the gain of the input voltage frequency is hardly change by the frequency. |
