| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-pass filter having a small circuit area and a small manufacturing variance even when a cut-off frequency is low. SOLUTION: A filter circuit comprises a capacitor 1 connected between an input terminal IN and an output terminal OUT of a signal, and constant- current circuits 2 and 3 of a MOS structure connected between a power source VDD and a ground. The output side node of the capacitor 1 is connected to intermediate node of the circuits 2 and 3 to constitute a filter. Thus, the cut-off frequency of the filter can be reduced by regulating a current value flowing to the circuits 2 and 3 without increasing a circuit area by using a capacitor having a large capacity value and a resistor having a large resistance value.
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