| 摘要 |
PURPOSE:To cancel automatically a DC offset voltage by providing an AND converter main body, a latch circuit, a subtractor circuit, an analog switch and a control circuit. CONSTITUTION:An external control signal on a signal line 113 goes to a low level during the operating and an analog switch 104 is thrown conversely to the position of an external input signal line 107 to the pause period. Thus, an input terminal 108 of an active filter 105 is connected to the position of the external input signal line 107. An output of the active filter 105 is converted into a data signal by the AD converter main body 101, sent to a signal line 115 and then a subtractor circuit 103. The subtraction circuit 103 subtracts an AD conversion data of an analog ground level stored in the latch circuit 102 during the pause period from the data and outputs the result of subtraction as the entire result of AD conversion. Thus, only a potential difference between the external input signal and the analog ground level is subject to AD conversion and the DC offset component is cancelled.
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