| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an offset that is changing during the operation and to minimize a time till a stable value is obtained after power-on by allowing the A/D converter to have a high pass filter and a filter coefficient control means that is connected to the high pass filter and generates a coefficient control signal to instruct revision of a variable filter coefficient during the operation. SOLUTION: The converter A is provided with aΔΣmodulator 1, a decimation filter 2, a high pass filter(HPF) 3, and a filter coefficient control section 4. The HPF 3 receives an output of the decimation filter 2 at its input and receives a signal to control a filter coefficient at its control input and produces an output of a result of applying high pass filter processing by a designated filter coefficient to the output of the decimation filter 2. An output of the filter coefficient control section 4 is given to a control input of the HPF 3, the filter coefficient control signal is fed to the HPF 3 during the operation of the converter A to select a proper coefficient for the HPF 3.
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