| 摘要 |
PROBLEM TO BE SOLVED: To automate adjustment of a cut-off frequency of a filter. SOLUTION: The filter adjustment circuit is provided with a filter 42 whose cut-off frequency is changed by digital data D48, a phase comparator circuit 41, a window comparator circuit 44 and a counter 48 that counts number of clocks PCK to generate the digital data D48. The digital data D48 are fed to a filter 19 whose characteristic is an object of adjustment as a characteristic adjustment signal. When an output signal S44 of the window comparator circuit 44 is settled within a specified range, an AND circuit 45 blocks the output signal S44 to stop counting of the counter 48 and a power supply circuit 52 stops consumption of operating power of the phase comparator circuit 41 and the window comparator circuit 44.
|
