| 摘要 |
PROBLEM TO BE SOLVED: To provide a gain-variable amplifier of a CMOS process meeting a wide dynamic range and high linearity while keeping NF satisfactory. SOLUTION: The gain-variable amplifier has: a plurality of initial stages LNA1-4 connected in parallel to one input terminal IN; the next stage LNA5 connected to the poststage; and a variable current source 20 that controls control currents IB1-IB4 allowed to flow to the initial stages LNA1-4 and keeps constant the total value of simultaneously flowing control currents. The output lines of the initial stages LNA1-4 preventing the control currents from flowing simultaneously are connected mutually to form a plurality of composite output lines L1, L2 and separately input them to a plurality of input ends of the next-stage amplifier 5. In the next-stage amplifier 5, each signal inputted from the plurality of input ends is amplified, and each amplified signal is added for output. COPYRIGHT: (C)2009,JPO&INPIT
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