Amplifiers – Signal feedback – Combined with control of bias voltage of signal amplifier
Patent
1974-12-02
1976-07-06
Rolinec, R. V.
Amplifiers
Signal feedback
Combined with control of bias voltage of signal amplifier
330 30D, H03G 330
Patent
active
039684539
ABSTRACT:
A signal to be controlled is applied to the base of an emitter-follower input transistor, the emitter of which is connected to an input terminal of a differential amplifier. This input terminal of the amplifier is connected by a diode to a controllable current source so that the base current of the differential amplifier input transistor is controlled. A constant current source is connected to the common emitter circuit of the differential amplifier, and the gain of the circuit is determined by the ratio of current in the latter source to current in the controllable source. A current conducting circuit, such as, an emitter load resistor, is connected to the emitter of the input transistor to hold the output impedance thereof at a substantially constant low value inspite of changes in the current of the controllable current source, Maximum gain of the circuit may be determined by separating the controllable current source into a controllable portion and a fixed portion in parallel so that the minimum current is at least as great as the current of the fixed portion. This limits the maximum circuit gain by limiting the maximum ratio of fixed current to controllable current. A fixed voltage source connected to the common circuit point between the controllable current source and the diode assures that the gain of the circuit will not fall below a selected minimum value.
REFERENCES:
patent: 2878380 (1959-03-01), Holmes
patent: 3764931 (1973-10-01), Waku et al.
Hongu Masayuki
Niimura Tsutomu
Dahl Lawrence J.
Eslinger Lewis H.
Rolinec R. V.
Sinderbrand Alvin
Sony Corporation
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