| 摘要 |
PROBLEM TO BE SOLVED: To provide a LNA (low noise amplifier) with gain switching capable of suppressing a deterioration in a noise figure. SOLUTION: The LNA with gain switching having a first transistor group (Q11 to Q18) and a second transistor group (Q21 to Q28) has a resistor R4 connected between the emitter of the transistor Q21 and the collector of a transistor Q1, and a resistor R5 connected to the emitters of the transistors Q22 to Q28 and the collector of the transistor Q1, having a resistor R5 composed of a resistance value being as 1/7 times as high as that of the resistor R4, and has no deterioration in a noise figure because isolation of the transistors Q21 to Q28, and the transistors Q1 and Q11 to Q18 which are turned off by the resistor R4 and the resistor R5 in a high gain mode is secured. COPYRIGHT: (C)2009,JPO&INPIT
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