US3876955A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Biasing circuit for differential amplifier
Assignee: RCA Corp
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Filing: 1973-07-16
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Granted: 1975-04-08
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Expires: 1993-07-16
Abstract
Abstract A circuit for establishing the quiescent bias current of a differential amplifier with active collector loads (transistor loads). The collector current of an auxiliary transistor, held at the same base-emitter potential as the active loads, is applied to the input circuit of a current amplifier which supplies from its output circuit the combined emitter currents of the differential amplifier transistors. The base currents of the auxiliary transistor and of the active load transistors are decoupled from the input circuit of the current amplifier so that variations in such currents do not affect the quiescent biasing of the differential amplifier.
Inventors
- 👤 Adel Abdel Aziz Ahmed
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:17
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/45; H03F3/45071
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
370 words
In a differential amplifier including means for supplying an operating potential between its first and second terminals; first and second amplifier devices of a first conductivity type, each of said amplifier devices having an input electrode and a common electrode and an output electrode, said common electrodes being coupled to a common node; and a first transistor of a second conductivity type complementary to said first conductivity type, said first transistor having a collector electrode connected to the output electrode of said first amplifier device so quiescent current can flow between them, said first transistor having an emitter electrode connected to the first terminal of said means for supplying an operating potential, said first transistor having a base electrode and a base-emitter junction between its base and emitter electrodes, a biasing circuit comprising: a second transistor being of said second conductivity type, having a collector electrode, having an emitter electrode connected to the first terminal of said means for supplying an operating potential, having a base electrode, and having a base-emitter junction between its base and emitter electrodes, proportioned to the base-emitter junction of said first transistor so that the transconductance of said second transistor is substantially twice that of said first transistor; a current amplifier having an input circuit connected between said second transistor collector electrode and the second terminal of said means for supplying an operating potential and for receiving solely the collector current of said second transistor, an output circuit connected between said common node and the second terminal of said means for supplying an operating potential and for determining the total level of current flow through said common node, and a current gain of substantially unity amplitude; and means for supplying between its first and second terminals a bias potential derived independently of the aforesaid connections, the first terminal of said means for supplying a bias potential being connected to the first terminal of said means for supplying an operating potential, the second terminal of said means for supplying a bias potential having the base electrodes of said first and said second transistors connected thereto, the poling of the biasing potential being such as to forward-bias the baseemitter junctions of said first and said second transistors.
Claim 2
Dependent Claim
370 words
In a differential amplifier including means for supplying an operating potential between its first and second terminals; first and second amplifier devices of a first conductivity type, each of said amplifier devices having an input electrode and a common electrode and an output electrode, said common electrodes being coupled to a common node; and a first transistor of a second conductivity type complementary to said first conductivity type, said first transistor having a collector electrode connected to the output electrode of said first amplifier device so quiescent current can flow between them, said first transistor having an emitter electrode connected to the first terminal of said means for supplying an operating potential, said first transistor having a base electrode and a base-emitter junction between its base and emitter electrodes, a biasing circuit comprising: a second transistor being of said second conductivity type, having a collector electrode, having an emitter electrode connected to the first terminal of said means for supplying an operating potential, having a base electrode, and having a base-emitter junction between its base and emitter electrodes, proportioned to the base-emitter junction of said first transistor so that the transconductance of said second transistor is substantially twice that of said first transistor; a current amplifier having an input circuit connected between said second transistor collector electrode and the second terminal of said means for supplying an operating potential and for receiving solely the collector current of said second transistor, an output circuit connected between said common node and the second terminal of said means for supplying an operating potential and for determining the total level of current flow through said common node, and a current gain of substantially unity amplitude; and means for supplying between its first and second terminals a bias potential derived independently of the aforesaid connections, the first terminal of said means for supplying a bias potential being connected to the first terminal of said means for supplying an operating potential, the second terminal of said means for supplying a bias potential having the base electrodes of said first and said second transistors connected thereto, the poling of the biasing potential being such as to forward-bias the baseemitter junctions of said first and said second transistors.
Claim 3
Dependent Claim
90 words
A biasing circuit as claimed in claim 1 wherein said means for supplying a bias potential comprises: a third transistor having a base electrode coupled to said second terminal of said means for supplying a bias potential, having an emitter electrode coupled to said first terminal of said means for supplying a bias potential, and having a collector electrode; a direct current feedback connection from the collector electrode to base electrode of said third transistor; and a current supply coupled between the emitter and collector electrodes of said third transistor.
Claim 4
Dependent Claim
252 words
A biasing circuit for an amplifier configuration including first and second transistors of a first conductivity type and a third transistor of a second conductivity type complementary to the first conductivity type, each said transistor having a base and an emitter and a collector electrode, said first and said second transistors being connected as an emitter-coupled differential amplifier, the collector electrodes of said first and said third transistors being connected so quiescent collector current is supplied by one of them to the other; said biasing circuit comprising: a fourth transistor of the same conductivity type as said third transistor, having a base electrode and an emitter electrode and a collector electrode; a current amplifier having an input circuit, which input circuit is direct current conductively connected to the collector electrode of said fourth transistor for receiving solely the collector current of said fourth transistor, and having an output circuit direct current conductively coupled to the emitter electrodes of said first and said second transistors, and having a current gain of substantially unity amplitude; means for deriving a bias potential independently of the aforesaid elements and for applying said bias potential between first and second points; and means including connections of the base electrodes of said third and said fourth transistors to said first point and connections of the emitter electrodes of said third and said fourth transistors to said second point for conditioning said third and said fourth transistors to respond to said bias potential with respective collector currents in 1:2 ratio.
Claim 5
Dependent Claim
252 words
A biasing circuit for an amplifier configuration including first and second transistors of a first conductivity type and a third transistor of a second conductivity type complementary to the first conductivity type, each said transistor having a base and an emitter and a collector electrode, said first and said second transistors being connected as an emitter-coupled differential amplifier, the collector electrodes of said first and said third transistors being connected so quiescent collector current is supplied by one of them to the other; said biasing circuit comprising: a fourth transistor of the same conductivity type as said third transistor, having a base electrode and an emitter electrode and a collector electrode; a current amplifier having an input circuit, which input circuit is direct current conductively connected to the collector electrode of said fourth transistor for receiving solely the collector current of said fourth transistor, and having an output circuit direct current conductively coupled to the emitter electrodes of said first and said second transistors, and having a current gain of substantially unity amplitude; means for deriving a bias potential independently of the aforesaid elements and for applying said bias potential between first and second points; and means including connections of the base electrodes of said third and said fourth transistors to said first point and connections of the emitter electrodes of said third and said fourth transistors to said second point for conditioning said third and said fourth transistors to respond to said bias potential with respective collector currents in 1:2 ratio.
Claim 6
Dependent Claim
80 words
A biasing circuit as claimed in claim 3 wherein said means for deriving and for applying a bias potential comprises: a current supply; a fifth transistor of the same conductivity type as said third and said fourth transistors, said fifth transistor having a base electrode and an emitter electrode respectively connected to said first and said second points and having a collector electrode coupled to said current supply; and means for applying direct coupled collector-to-base feedback to said fifth transistor.
Claim 7
Dependent Claim
68 words
A biasing circuit as claimed in claim 3 wherein said current amplifier comprises: fifth and sixth transistors of said first conductivity type having collector electrodes direct current conductively coupled respectively to said fourth transistor collector electrode and to the emitter electrodes of said first and said second transistors, having base electrodes direct coupled from said fifth transistor collector electrode, and having emitter electrodes connected to a reference potential.
Claim 8
Dependent Claim
63 words
A bias circuit as set forth in claim 3 wherein said means for deriving and for applying a bias potential and applying the same between said first and said second points comprises: semiconductor diode means connected between said first and said second points; and means applying forward bias current to said semiconductor junction, to develop said bias potential across said semiconductor diode means.
References Cited (Backward Citations)
US3719833A
Cited
US3760288A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-07 | 1978-10-07 | 1979-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-07 | 1982-10-07 | 1983-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-07 | 1986-10-07 | 1987-04-08 | $7700.00 | Window Closed / Lapsed |