Patent US4280091A successfully refreshed from Google Patents.
US4280091A
Expired / Lapsed
US
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Variable current source having a programmable current-steering network
Assignee: St Clair Intellectual Property Consultants Inc
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Filing: 1979-10-29
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Granted: 1981-07-21
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Expires: 1999-10-29
Abstract
Abstract A variable current source having a programmable current-steering network is provided in which a plurality of field-effect transistors both provide current switching and form an integral part of the current source. This is accomplished by switching the field-effect transistors into and out of the feedback loop of a voltage follower, which in turn is connected to a current-setting resistor. Reference voltage for the current-setting resistor is provided by a variable voltage generator. The field-effect transistors are switched by means of a programmable digitally-switched bias generator circuit.
Inventors
- 👤 David F. Hiltner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:03
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/468
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
125 words
A current source for providing current to a plurality of output nodes, comprising: a voltage follower comprising an operational amplifier having inverting and non-inverting inputs and an output, wherein said output is coupled to said inverting input to thereby provide an output loop; a current-setting resistor connected to said inverting input; a voltage generator connected to said non-inverting input to provide a reference voltage for said current-setting resistor; a plurality of field-effect transistors switchable into and out of said output loop, said field-effect transistors being associated with respective ones of said plurality of current output nodes and being adapted to conduct substantially all of the current produced by said current-setting resistor; and means for switching said field-effect transistors into and out of said output loop.
Claim 2
Dependent Claim
125 words
A current source for providing current to a plurality of output nodes, comprising: a voltage follower comprising an operational amplifier having inverting and non-inverting inputs and an output, wherein said output is coupled to said inverting input to thereby provide an output loop; a current-setting resistor connected to said inverting input; a voltage generator connected to said non-inverting input to provide a reference voltage for said current-setting resistor; a plurality of field-effect transistors switchable into and out of said output loop, said field-effect transistors being associated with respective ones of said plurality of current output nodes and being adapted to conduct substantially all of the current produced by said current-setting resistor; and means for switching said field-effect transistors into and out of said output loop.
Claim 3
Dependent Claim
53 words
A current source in accordance with claim 1 wherein said switching means comprises a plurality digitally-switched bias generators coupled to respective ones of said plurality of field-effect transistors, said bias generators being programmable to selectively switch only one at a time of said plurality of field-effect transistors into said operational amplifier output loop
Claim 4
Dependent Claim
34 words
A current source in accordance with claim 2 wherein each of said bias generators comprises a switched current source and a bias resistor connected to the gate of each of said field effect transistors.
Claim 5
Dependent Claim
24 words
A current source in accordance with claim 1 wherein said voltage generator is adjustable to provide a variable reference voltage for said current-setting resistor.
References Cited (Backward Citations)
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US3947704A
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US4163188A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-07-20 | 1985-01-19 | 1985-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-07-20 | 1989-01-19 | 1989-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-07-20 | 1993-01-19 | 1993-07-21 | $7700.00 | Window Closed / Lapsed |