| 摘要 |
PROBLEM TO BE SOLVED: To simplify the circuit constitution by decreasing the number of pins when a low-noise amplifier (LAN) circuit is constituted in an LSI and to suppress the input/output loss of an RF signal due to the switching of the circuit by compensating impedance, which is set at weak input time, at intense input time. SOLUTION: The LNA 1 and SW1 and SW2 which electrically connect its input and output to each other are provided on the same IC chip, and input/ output matching circuits 2 and 3 and a compensating circuit for impedance are additionally provided to the IC chip. This constitution requires only three pins of the IC chip. At weak input time, constants of the output matching circuits 2 and 3 are set to match impedance and when the circuit is switched at intense input time, the mentioned matching is compensated by the compensating circuit 4 to suppress the input/output loss of the RF signal. This compensation is carried out by setting the constant of the compensating circuit 4 so that the impedance of the parallel circuit composed of the LNA 1, input/output matching circuits 2 and 3, etc., resonate in a received signal band.
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