| 摘要 |
PROBLEM TO BE SOLVED: To implement a filter small in chip size, easy to design and excellent in frequency characteristic.SOLUTION: A filter circuit includes: a Gm-C filter including a Gm amplifier and a capacitive element; a filter control signal generation circuit for generating a control signal for controlling a characteristic thereof; and adjustment means for controlling a current flowing through input MOSTr of the Gm amplifier. The filter control signal generation circuit includes: a MOS Tr pair comprising first MOS Tr of a first conductivity type having a drain and a gate connected together, and second MOS Tr of the first conductivity type having a gate connected to that of first MOS Tr; a MOS Tr pair comprising third MOS Tr of a second conductivity type having a drain connected to that of first MOS Tr, and fourth MOS Tr of the second conductivity type having a drain and a gate connected together, the gate connected to that of third MOS Tr, and the drain connected to that of second MOS Tr; and a resistive element connected to any one source of first to fourth MOS Tr. |
