Amplifiers – With semiconductor amplifying device – Including gain control means
Patent
1982-01-19
1984-09-11
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including gain control means
330284, 330 86, 330145, H03G 330
Patent
active
044713240
ABSTRACT:
A signal gain controlled system comprises an operational amplifier including a feedback path between the input and output terminals of the amplifier. The system includes first variable impedance means for varying the output voltage at the output terminal of the amplifier in response to and as a function of the input current signal applied to the input terminal and a first control signal. A signal path coupled between the output terminal of the operational amplifier and the output terminal of the system includes second variable impedance means for varying the output current of the system in response to and as a function of (a) the output voltage at the output of the amplifier and (b) a second control signal. The signal gain of the system is a function of the ratio of the second and first control signals.
The preferred amplifier is the type having an input resistance and a feedback resistance, wherein at least one of the resistances includes a transistor which is biased to operate in its saturated region. The gain of the amplifier is a function of the control signal applied to the base of the saturated transistor.
The signal gain controlled system can be utilized with a level sensing detector to provide signal compression or expansion.
REFERENCES:
patent: 3676789 (1972-07-01), Bray
patent: 3700918 (1972-10-01), Kawashima
patent: 3919654 (1975-11-01), Toumani
patent: 4053846 (1977-10-01), Acker
Corinth, "Low Frequency Instrumentation Amplifier with Logarithmic Steps of Amplification," Funkschan, No. 17, 1981.
DBX Inc.
Mullins James B.
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