| 摘要 |
PURPOSE:To prevent gain reduction at a high frequency region by connecting respectively a positive feedback resistor and a negative feedback resistor from the drain of the 2nd and 3rd stage of FETs of three-stage connection to the gate of the 1st stage via a coupling capacitor. CONSTITUTION:A positive feedback path from the gate of the 2nd stage to that of the 1st stage is not provided in a conventional three-stage negative feedback amplifier circuit and the gain reduction at a high frequency region of >=1GHz is remarkable, and in connecting a resistor R8 and a capacitor C5 between the drain of an FETQ2 and a gate of the 1st FETQ1 to form a positive feedback path, then gain keeping is attained at a region of 1-2GHz. Thus, the region whose gain is decreased by 3dB conventionally is extended from 1.2GHz to 2.2GHz and high gain at a high frequency region is attained.
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