Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1980-03-26
1982-05-25
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330252, 358174, H03F 345
Patent
active
043319297
ABSTRACT:
A gain-controlled amplifier comprises first and second transistors connected in common-emitter configuration, third and fourth transistors connected in common-emitter configuration, a driver circuit responsive to application of an input signal thereto to vary the common-emitter current of the first and second transistors and common-emitter current of the third and fourth transistors in opposite phase relation with respect to each other, and an output circuit connected to the collectors of one of a first pair of the first and fourth transistors and a second pair of the second and third transistors for producing an output signal corresponding to the difference between the collector currents of the one pair of transistors. A control signal is applied between commonly connected bases of the first transistor pair and commonly connected bases of the second transistor pair. When the gain of the gain-controlled amplifier is set small, the collector currents of the transistors connected to the output circuit become small so that noise output voltage is reduced. In order to further reduce noise output voltage, an equal number (one or more) of PN junctions may be connected in series in the respective emitter circuits of the first to fourth transistors.
REFERENCES:
patent: 3619486 (1971-11-01), Tzakis
patent: 3684974 (1972-08-01), Solomon et al.
patent: 3761741 (1973-09-01), Hoeft
patent: 3961360 (1976-06-01), Sato et al.
Mullins James B.
Nippon Gakki Seizo Kabushiki Kaisha
Wan Gene
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