Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2000-02-09
2001-10-09
Pascal, Robert (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S256000, C327S359000
Reexamination Certificate
active
06300832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gain variable amplifier apparatus.
2. Description of the Related Art
A first prior art gain variable amplifier apparatus is formed by a single stage gain variable amplifier. This will be explained later in detail.
In the above-described first prior art gain variable amplifier apparatus, however, the region of linear gain characteristics is narrow, and also, the gain is dependent upon the thermal voltage.
A second prior art gain variable amplifier apparatus is formed by three stages of gain variable amplifiers connected in series (see JP-A-8-46463). The reference voltages of the gain variable amplifiers are made different from each other to obtain a total gain having a wider linear relationship. This also will be explained later in detail.
The above-described second gain variable amplifier apparatus, however, needs a plurality of gain variable amplifiers to achieve a wider gain control range, which would increase the power consumption.
SUMMARY OF THE INVENTION
It is an object of the present invention to compensate for the thermal voltage component in the gain characteristics.
Another object is to enlarge the region of the linear gain control relationship of the gain characteristics.
According to the present invention, in a gain variable amplifier apparatus, a thermal voltage proportional circuit converts a first control voltage into a second control voltage proportional to a thermal voltage, and the gain of a gain variable amplifier is controlled by the second control voltage. Thus, the thermal voltage component in the gain characteristics is compensated for.
Also, in a gain variable amplifier apparatus, a control voltage correction circuit including a plurality of differential amplifiers having different inflection point characteristics converts a first control voltage into a second control voltage, and the gain of a gain variable amplifier is controlled by the second control voltage. Thus, the linear relationship of the gain characteristics becomes wider.
REFERENCES:
patent: 5910751 (1999-06-01), Winn et al.
patent: 6020786 (2000-02-01), Ashby
patent: 6072366 (2000-02-01), Maeda et al.
patent: 57-127311 (1982-08-01), None
patent: 63-309010 (1988-12-01), None
patent: 64-57828(01) (1989-03-01), None
patent: 1-241207 (1989-09-01), None
patent: 3-173210 (1991-07-01), None
patent: 8-46463 (1996-02-01), None
patent: 9-502316 (1997-03-01), None
Japanese Office Action dated Jan. 4, 2000 with partial translation.
Paul R. Gray et al., “Analysis and Design of Analog Integrated Circuits”,John Wiley & Sons, Inc., pp. 667-675, 1997.
Choe Herny
McGinn & Gibb PLLC
NEC Corporation
Pascal Robert
LandOfFree
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