| 摘要 |
PURPOSE:To obtain a digital filter output signal having a prescribed amplitude not affected by an amplitude level of an input signal by controlling the amplitude of the input signal to the digital filter. CONSTITUTION:When a bit next to the MSB is logical high in an output 14 of a digital LPF13, a serial PCM signal 3 is inputted to the digital filter 7 while keeping X 1-time, and the signal is filtered. When the 2nd bit from the MSB is logical high in the output 14, since an output of an AND circuit 29 gives a high level to a control terminal of a 3-state buffer circuit 21, the PCM serial input 3 is multiplied by two and the result is inputted to the digital filter 7. Thus, even if the input amplitude level of the PCM serial input 3 is changed, an output filtering signal having a prescribed amplitude is obtained at digital filter outputs 8 and 10. |
