Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1988-05-02
1989-08-01
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330257, 330261, 358190, H03F 345
Patent
active
048536474
ABSTRACT:
A first pair of transistors, Q721 and Q723, operating, each, as an emitter follower, has a relatively low emitter current. The emitter followers drive corresponding base electrodes of transistors of a second pair of transistors, Q148 and Q149, coupled as a differential amplifier. A current gain compensating transistor Q726 has a current gain that tracks current gain variations of each of the transistors of the second pair. A base electrode current of the compensating transistor and a second current i.sub.Q727 that is unaffected by current gain variations are summed. The summed current is coupled via transistors Q722 and Q724 of a current mirror arrangement to first and second junction terminals, 610e and 610f. The junction terminals are coupled between the respective emitter electrodes of the emitter followers and the base electrodes of the second pair. Currents generated by the current mirror arrangement compensate for variations in the base currents in the transistors of the second pair so as to maintain the emitter currents in the emitter followers substantially unaffected by these variations.
REFERENCES:
patent: 3668541 (1972-06-01), Pease
patent: 3878471 (1975-04-01), Ahmed
patent: 3891935 (1975-06-01), Limberg
patent: 3938054 (1976-02-01), Leidich
patent: 4714871 (1987-12-01), Craft et al.
Craft Jack
Low Michael L.
Henig S. S.
Laks J. J.
Mullins James B.
RCA Licensing Corp.
Whitacre E. M.
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