| 摘要 |
PURPOSE:To make the noise coefficient and the intermodulation distortion characteristic compatible to some degree by switching a gain in a high frequency amplifier circuit and an attenuation in an attenuation circuit of a 2nd intermediate frequency stage interlockingly. CONSTITUTION:A high frequency amplifier circuit 26 whose gain is switched into two stages (a prescribed gain and O dB) by a switching signal SW given to a switching terminal 30 is inserted just the post-stage of a high frequency amplifier circuit 6 in a high frequency amplifier stage. Moreover, an attenuation circuit 28 is inserted to just the post-stage of the 2nd intermediate frequency amplifier circuit 22 of the 2nd intermediate frequency stage in a way that the attenuation is the same as the gain of the high frequency amplifier circuit 26 when the gain of the circuit 26 is a prescribed value or the attenuation is O dB when the gain of the circuit 26 is O dB interlockingly.
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