| 摘要 |
PROBLEM TO BE SOLVED: To continuously adjust a circuit provided with a switched capacitor like a ladder type filter. SOLUTION: For this integrated circuit provided with the switched capacitor, the switched capacitor is realized as a DC insulation variable capacitor. The DC insulation variable capacitor is realized as a T structure provided with three capacitors and one of the three capacitors is realized together with a buffer amplifier. The buffer amplifier receives control signals and inputs buffered control signals to an active device provided with capacitance depending on the level of the buffered control signals. For instance, the capacitor C2 of the T structure is realized by using a voltage control buffer 402 and a varactor diode 404. The buffer 402 is a high impedance output buffer for providing insulation and adjusting or increasing/decreasing a control voltage beforehand.
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