| 摘要 |
PROBLEM TO BE SOLVED: To reduce the input-converted noise of a filter circuit. SOLUTION: This filter circuit is provided with plural element circuits, composed of divided filter circuits so as to include at least one voltage control current source. At least one of these plural element circuits is an amplifying element circuit, provided with an amplifying function for amplifying signals inputted to the filter circuit with a preset amplification factor. Then, the amplifying circuit is provided with a loop circuit composed of plural in-loop voltage control current sources setting mutual conductance values into prescribed correspondent relation and a correspondent capacitor, which is connected to a contact inside the loop circuit, having a capacitance value which depends on the correspondent relation, so that the potential of the contact can become a prescribed potential corresponding to the amplification factor. The amplifying element circuit is provided with electrical characteristics which do not depend on the amplification factor from the view point of the input side of the filter circuit.
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