PURPOSE: To improve precision for an output signal level by adding a register for setting the kind of an input signal and a means to correct an average value for the absolute value of the input signal corresponding to the kind.

CONSTITUTION: The mode of the input signal is set from the outside to a mode setting register 106. Corresponding to the kind of the input signal to be set to this register 106, a correcting value is inputted from a correcting value controller 107 to a multiplier 103. Since the output of the multiplier 103 is made equivalent to the root of the power average value of the input signal by this multiplication, the output of a multiplier 104 can be defined as proper gain for setting the square average value of the output signal at a desired standard value. Thus, the precision for the output signal level can be improved with simple configuration.