Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1992-03-05
1993-07-20
Pascal, Robert J.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330282, 330259, H03F 345
Patent
active
052297209
ABSTRACT:
A VCA circuit is used at an input stage of communication device, an OA device or the like. The VCA circuit includes an output varying circuit which distributes a current supplied from a power supply side in accordance with a predetermined coefficient. The VCA circuit also includes an operational amplifier provided on an input side of the output varying circuit, and a feedback resistor connected between one of two input terminals and an output terminal of the operational amplifier. An input signal is applied to one of the two input terminals of the operational amplifier, a signal output from the output varying circuit is applied to the other input terminal. An output signal of the VCA circuit is drawn from the output terminal of the operational amplifier. An offset current generated in the output varying circuit can be reduced by varying the predetermined coefficient since the operational amplifier and the feedback resistor are provided on the input side of the output varying circuit and the output signal of the output varying circuit is applied to one of the two input terminals of the operational amplifier.
REFERENCES:
patent: 3736520 (1973-05-01), Acker
patent: 4227095 (1980-10-01), Bazil
patent: 4366446 (1982-12-01), Henderson et al.
patent: 5121080 (1992-06-01), Scott, III et al.
Dinh Tan
Pascal Robert J.
Pioneer Electronic Corporation
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