| 摘要 |
PROBLEM TO BE SOLVED: To provide a gain variable high frequency amplifier circuit with low distortion and whose noise characteristic is not deteriorated even when the amplifier circuit is used for an input signal with a high power dynamic range. SOLUTION: A transmission line 20 for configuring a distributed constant circuit of an input matching circuit 12 and a transmission line 42 for configuring a distributed constant circuit of an output matching circuit 34 are connected to the variable high frequency amplifier circuit by a switch 50 that can select interconnection of the lines 20, 42 or disconnection of the lines 20, 42. In the case of closing the switch 50 and inactivating an FET 22, since an input signal is outputted while being passing through the switch 50, the gain can be changed in comparison with the case of opening the switch 50 and allowing the FET 22 to amplify the input signal.
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