Amplifiers – With semiconductor amplifying device – Including gain control means
Patent
1996-05-30
1998-02-24
Mottola, Steven
Amplifiers
With semiconductor amplifying device
Including gain control means
330284, H03G 312
Patent
active
057215138
ABSTRACT:
An input signal is applied to a first input terminal of a differential amplifier through an input resistance, and a feedback signal is applied to the first input terminal through a feedback resistance. A reference potential is applied to a second input terminal of the differential amplifier. A capacitance element is connected between the second input terminal and a high potential power supply, and a capacitance element is connected between the second input terminal and a low potential power supply. The amplification ratio of an amplification circuit can be switched over multiple stages by switching the resistance values of the input resistance and the feedback resistance by semiconductor analog switches. When any fluctuation exists in a power supply voltage, the fluctuation component is applied to the first input terminal of the differential amplifier through the semiconductor analog switches and causes a fluctuation of the amplification ratio. This fluctuation component of the power supply voltage is applied to the second input terminal from the capacitance element connected to the second input terminal. Since the differential amplifier eliminates the in-phase component of the signal applied to the second input terminal, the influence of the fluctuation of the power supply voltage on the input signal can be restricted because the capacitance element is connected to the second input terminal.
REFERENCES:
patent: 4068185 (1978-01-01), Christen et al.
patent: 4350959 (1982-09-01), Rosenbaum
patent: 4754224 (1988-06-01), Maschek et al.
patent: 4855685 (1989-08-01), Hochschild
patent: 5138280 (1992-08-01), Gingrich et al.
patent: 5406636 (1995-04-01), Yamada et al.
Patent Abstracts of Japan, vol. 10, n. 95 (E-395), 12 Apr. 1986 JP 60 2365009 A (Fujitsu K.K.), 25 Nov. 1985, abstract.
Fujitsu Limited
Mottola Steven
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