| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable gain amplifier employing a composite CMOS circuit the gain of which can be controlled over a wide range, which is utilized as a mixer circuit or the like, and the bias applied to which is always made constant. SOLUTION: In a composite CMOS type gm variable circuit 10, a gate and a drain of an NMOS transistor 11 are connected together, and a gate and a drain of a PMOS transistor 14 are connected together. The composite transistor 15 is configured by connecting a source of the NMOS transistor 11 to a source of a PMOS transistor 12, the composite CMOS transistor 16 is configured by connecting a source of the PMOS transistor 14 to a source of an NMOS transistor 13, and a variable current source 30 is connected in parallel with the composite CMOS circuit 17 comprising the series connection of the composite PMOS transistor 15 and the composite NMOS transistor 16. A composite CMOS type gm variable circuit 20 located opposite to the circuit 10 is similarly configured, and input signals whose polarities are opposite to each other are respectively applied to both the circuits 10, 20. COPYRIGHT: (C)2007,JPO&INPIT
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