PURPOSE: To adapt the titled filter to a monolithic IC by connecting an interpolation circuit to the output side of a switched capacitor filter (SCF) and outputting an output of the SCF and an output of the interpolation circuit switchingly.

CONSTITUTION: A switch 4 is thrown to make the contact 41 to ON state and an output from the itnerpolation circuit 3 is outputted to an output terminal 10 of the system, and on the other hand, the other contact 42 is closed to output the output of the SCF 2 to the output terminal 10 of the system directly. Moreover, a clock signal generating circuit 6 selecting one of different clock signals and outputting the result to the SCF 2 is connected via a connecting point 7 and the clock signal generating circuit 6 gives a signal of low frequency in the clock signal to an interpolation circuit 3 through a connection 8. For example, one of the clock signals of frequency fs or 2fs from the clock signal generating circuit 6 via a connection 7 is selected and the result is outputted to the SCF 2 and a clock signal of a low frequency fs is outputted to the interpolation circuit 3 via a connection 8. Thus, the monolithic IC is realized.