Amplifiers – With semiconductor amplifying device – Including gain control means
Patent
1977-11-28
1978-09-26
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including gain control means
330288, 330300, H03G 330, H03F 304
Patent
active
041174160
ABSTRACT:
A current mirror amplifier (CMA) has master and slave mirroring transistors of bipolar type, input and output terminals to which the collector electrodes of the master and slave mirroring transistors respectively connect, and a common terminal to which the emitter electrodes of the mirroring transistors connect. The master mirroring transistor is provided with collector-to-base feedback for applying base potential to it which conditions its collector-to-emitter path to conduct input current applied between the common and input terminals of the CMA. The current gain of the CMA as between its input and output terminals is determined by the ratio of the transconductance of the slave mirroring transistor to that of the master mirroring transistor, whenever the base potential of the master mirroring transistor is applied to the base electrode of the slave mirroring via a transmission gate rendered transmissive responsive to a first level control potential being applied thereto. In furtherance of matching the base potentials of the master and slave mirroring transistors, so this relationship obtains, a second transmission gate is included in the collector-to-base feedback connection of the master mirroring transistor and is rendered transmissive by application of said first level of potential to it, whereby an offset potential is provided across said second transmission gate compensating for the offset potential across said first transmission gate insofar as effects on CMA current gain is concerned. Responsive to a second level of control potential applied to it the first transmission gate is rendered non-transmissive and current gain between the input and output terminals falls to zero.
REFERENCES:
patent: 3973215 (1976-08-01), Ahmed
Christoffersen H.
Limberg A. L.
Mullins James B.
RCA Corporation
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