| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable active inductor that is not varied in output current noise. SOLUTION: The active inductor connects in parallel a capacitance element and an element connected in series to a switch between the gate and source of a transistor. Namely, this inductor connects the drain of PMOS transistor M2 and the one terminal of capacitor C1. Moreover, the one terminal of switch S1 is connected in series to a terminal Vin and the other terminal of capacitor C1 and the other terminal of switch S1 is connected to the gate of PMOS transistor M2. An inductance value is varied by changing a virtual gate-to-source capacitance of the transistor by opening or closing the switch S1. In this case, mutual conductance of the MOS transistors M1, M2 does not change, so that the output current noise is not varied. COPYRIGHT: (C)2010,JPO&INPIT
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