| 摘要 |
PURPOSE:To convert a digital signal into an analog data without DC components by extracting a low frequency signal component of the analog data of a level shift circuit with a low frequency filter circuit and controlling the amount of shift based on the level amount of the component. CONSTITUTION:The low frequency filter circuit 18 extracts a frequency signal component of <=20Hz from the analog data outputted from a level shift circuit 14, compares the level of the extracted frequency signal with a ground potential (0 level) and outputs a signal having a level corresponding to the difference. Then, the level shift circuit 14 compares a signal level outputted from the low frequency filter circuit 18 with the level of the analog data outputted from a buffer circuit 13 so as to shift the level, resulting that the difference becomes zero, i.e., the DC component of the analog data is eliminated. |
