| 摘要 |
PURPOSE:To attain automatic adjustment of a filter characteristic, to attain time reduction of a filter adjustment and high accuracy by making the filter characteristic adjustable in a double integration filter circuit and providing a switch to switch the Q value of the filter and switching the switch at the filter adjustment. CONSTITUTION:A series circuit comprising a resistor R3 and a switch SW is connected to parallel with a resistor R1. The feedback rate of a feedback circuit 15 is switched in response to the on/off of the switch SW and only the Q value of the filter is switched. The switch SW is turned off at the normal use and the switch SW is turned on at filter adjustment and the characteristic is switched to the BPF characteristic with large Q value to be illustrated in imaginary lines in figure. Simultaneously, as to the output signal from an output terminal 17, a peak is detected and the peak frequency f0 is made coincident with the prescribed object frequency. Thus, the sharpness of the peak is increased to attain ease of filter adjustment with high accuracy.
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