| 摘要 |
PURPOSE:To reduce a ripple in an analog signal after conversion into the analog signal by increasing the duty ratio of a pulse by a DA converter and also by increasing its repetitive frequency. CONSTITUTION:When a power source is put to work, an initial value setting circuit 17 presets current sound volume in an up-down counter 15. To increase the sound volume, the up-down counter 15 counts up clock pulses frequency-divided by a frequency divider 14 as prescribed under a volume-up command and only a control pulse signal, such as a signal P10, switched by the output of a detector 22 is converted into an analog value, which is sent out from an output terminal 24 to control the sound volume to a prescribed value. |
