| 摘要 |
PROBLEM TO BE SOLVED: To match impedances between stages of a plurality of amplifiers in an amplifying circuit, constituted by connecting the plurality of amplifies in the stages, without increasing the circuit size. SOLUTION: In the amplifying circuit comprising the amplifiers of front and rear stages, the amplifier 1 of the front stage is a variable gain differential amplifier including a Gilbert cell circuit. An input signal is supplied to the Gilbert cell circuit 20. Then nMOS transistors M7 and M8 are cascaded to the Gilbert cell circuit. A source voltage Vcc is applied to drains of nMOS transistors M7 and M8 through inductors L1 and L2. A pair of output terminals are connected to the drains of the nMOS transistors M7 and M8. Parasitic capacities of the nMOS transistors M7 and M8 are adjusted to match the output impedance of the amplifier 1 to the input impedance of the amplifier of the rear stage. COPYRIGHT: (C)2007,JPO&INPIT
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