Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1982-09-27
1985-05-07
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330257, H03G 330, H03F 345
Patent
active
045160813
ABSTRACT:
A voltage controlled variable gain circuit suitable for construction as an integrated circuit includes a first current divider comprised of two NPN transistors; a second current divider comprised of two NPN transistors, a control voltage for setting the gain of the circuit being supplied to the bases of a transistor of each current divider; an operational amplifier for producing a first signal in response to an input current, and output currents from each current divider; first and second current sources, each producing a constant current; a first differential amplifier comprised of two NPN transistors having emitters supplied with the constant current from the first current source and the collector of one transistor supplying a drive current to the first current divider; and a second differential amplifier comprised of two NPN transistors having emitters supplied with the constant current from the second current source and the collector of one transistor supplying a drive current to the second current divider; the steady state currents through both first and second current dividers being controlled to a value less than one-half the value of the constant current from the first and second current sources, by constructing the emitter areas of the other transistors of each differential amplifier to be N times larger than the emitter areas of the one transistors thereof; or by supplying offset voltages to the bases of the transistors of both differential amplifiers; or by connecting the emitters of the two transistors of each differential amplifier with a resistive element.
REFERENCES:
patent: 4422051 (1983-12-01), Katakura et al.
Eslinger Lewis H.
Mullins James B.
Sinderbrand Alvin
Sony Corporation
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