| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration in noise index due to a signal leak from a base terminal and an emitter terminal of a high-frequency amplifier formed on a semiconductor substrate toward the substrate. SOLUTION: In the high-frequency amplifier which can vary AC, an impedance element 60 and an impedance element 61 use metal wires of low resistivity of aluminum, copper, etc., and vary in wire length, wire width, and wire shape and a diffusion capacitor 50 varies in area to vary impedance to a high-frequency signal. The impedance element 60, diffusion capacitor 50, and impedance element 61 reduce the AC impedance to the high-frequency signal and a signal path is formed from the base terminal of a first transistor 15 to an external ground terminal through the emitter terminal. Consequently, signal components to pass through the insulating film capacity of an insulating film of a semiconductor substrate to the reverse side of the substrate in the high-frequency signal input to a pad 20 for the base terminal from outside are reduced or blocked to eliminate a signal leak to the reverse side of the substrate, thereby to prevent deterioration in noise index. COPYRIGHT: (C)2007,JPO&INPIT
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