| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-noise amplifier capable of being operated without causing serious route loss even in the case that abnormality is generated in a main amplifier circuit and it can not be normally operated by providing at least one standby circuit arranged parallelly to the main amplifier circuit. SOLUTION: A control signal generation circuit 42 monitors whether or not a first amplifier circuit 24 is abnormally operated and generates the switching control signals different in level in accordance with a monitored result. A first switch 22 supplies signals from an input impedance matching circuit 20 to the first amplifier circuit 24 or the standby circuit 30 corresponding to the switching control signals. When the first amplifier circuit 24 is abnormally operated, the signals from the input impedance matching circuit 20 are supplied to the standby circuit 30. The standby circuit 30 uses a microstrip transmission line 32 and acts as a low loss route. A second switch 38 supplies the signals outputted from the first amplifier circuit 24 or the standby circuit 30 to an output impedance matching circuit 40 based on the switching control signals.
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