US3918005A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Operational amplifier circuitry with automatic self-biasing for enhanced voltage compliance
Assignee: AT&T Inc
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Filing: 1974-07-24
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Granted: 1975-11-04
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Expires: 1994-07-24
Abstract
Abstract In a circuit configuration of two tandemly connected operational amplifiers either controlled current or controlled voltage is provided at a load impedance connected across the inverting input and the output of the second operational amplifier. The signal being controlled is independent of the value of the load impedance. The voltage compliance across the load impedance is enhanced by the addition of a pair of feedback loops connected around the tandemly coupled operational amplifiers.
Inventors
- 👤 Stanley Bruckenstein
- 👤 Barry Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:03
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/461
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
204 words
Operational amplifier circuitry for maintaining a controlled signal level at a variable, floating load impedance with an enhanced voltage compliance across the load impedance, the circuitry including: a first operational amplifier having inverting and noninverting inputs and an output, said load impedance having one terminal which is responsive to signal variations from said first operational amplifier output and another terminal which is responsive to signal variations at said inverting input of said first operational amplifier, means for supplying a variable control voltage signal, a second operational amplifier having inverting and noninverting inputs and an output, said noninverting input being maintained at a reference ground potential, a first resistor serially connecting said variable control voltage signal supply means to said second operational amplifier inverting input, means for coupling a portion of said output from said second operational amplifier back to its inverting input, a second resistor serially connecting said second operational amplifier output to said first operational amplifier inverting input, inverting circuitry for coupling an inverted variable signal reference from the output of said first operational amplifier back to its noninverting input, and means for coupling a portion of the output signal from said first operational amplifier back to said second operational amplifier inverting input.
Claim 2
Dependent Claim
204 words
Operational amplifier circuitry for maintaining a controlled signal level at a variable, floating load impedance with an enhanced voltage compliance across the load impedance, the circuitry including: a first operational amplifier having inverting and noninverting inputs and an output, said load impedance having one terminal which is responsive to signal variations from said first operational amplifier output and another terminal which is responsive to signal variations at said inverting input of said first operational amplifier, means for supplying a variable control voltage signal, a second operational amplifier having inverting and noninverting inputs and an output, said noninverting input being maintained at a reference ground potential, a first resistor serially connecting said variable control voltage signal supply means to said second operational amplifier inverting input, means for coupling a portion of said output from said second operational amplifier back to its inverting input, a second resistor serially connecting said second operational amplifier output to said first operational amplifier inverting input, inverting circuitry for coupling an inverted variable signal reference from the output of said first operational amplifier back to its noninverting input, and means for coupling a portion of the output signal from said first operational amplifier back to said second operational amplifier inverting input.
Claim 3
Dependent Claim
139 words
The operational amplifier circuitry in accordance with claim 1 wherein the signal level being controlled is an electrIcal current through said load impedance, said current being held at a constant level regardless of the value said load impedance takes on over a predetermined range of values up to the ratio of the enhanced compliance voltage to the controlled current, and said means for coupling a portion of said second operational amplifier output back to its inverting input comprises a third resistor, the ratio of said third resistor value to the product of said first and second resistor values providing a proportionality constant which, in conjunction with said variable control voltage signal, controls the amount of current delivered to said first operational amplifier inverting input independent of the value said load impedance takes on over said predetermined range of values.
Claim 4
Dependent Claim
84 words
The operational amplifier circuitry in accordance with claim 2 wherein the inverting circuitry includes a third operational amplifier having inverting and noninverting inputs and an output, said noninverting input being maintained at a reference ground potential and said output being connected to said first operational amplifier noninverting input, a fourth resistor connecting said output of said first operational amplifier to said inverting input of said third operational amplifier, and a fifth resistor connecting said output of said third operational amplifier to its inverting input.
Claim 5
Dependent Claim
105 words
The operational amplifier circuitry in accordance with claim 3 wherein the means for coupling a portion of the output signal from the first operational amplifier back to the control current signal supply means comprises a sixth resistor connected between said output of said first operational amplifier and said inverting input of said second operational amplifier, the ratio of resistor values of said fifth resistor to said fourth resistor being approximately equal to the ratio of resistor values of said third resistor to said sixth resistor to effect enhanced voltage compliance across said load impedance while maintaining said predetermined control current signal through said load impedance.
Claim 6
Dependent Claim
114 words
The operational amplifier circuitry in accordance with claim 1 wherein the signal level being controlled is an electrical voltage at any point in said load impedance, and same means for coupling a portion of the output from the second operational amplifier back to its inverting input includes a third resistor, said third resistor comprising a separable portion of said load impedance, a third operational amplifier having an inverting and a noninverting input and an output, said output being directly coupled to said inverting input and said third resistor coupled to said third operational amplifier noninverting input, and a fourth resistor connected between said third operational amplifier output and said second operational amplifier inverting input.
Claim 7
Dependent Claim
99 words
The operational amplifier circuitry in accordance with claim 5 wherein the inverting circuitry for coupling the output of the first operational amplifier to its noninverting input includes a fourth operational amplifier having an inverting and a noninverting input and an output, said noninverting input being maintained at a reference ground potential and said output being connected to said first operational amplifier noninverting input, a fifth resistor connecting said output of said first operational amplifier to said inverting input of said fourth operational amplifier, and a sixth resistor connecting said output of said fourth operational amplifier to its inverting input.
Claim 8
Dependent Claim
173 words
The operational amplifier circuitry in accordance with claim 5 wherein the means for coupling a portion of the output signal from the first operational amplifier back to the control current signal supply means includes a fourth operational amplifier having an inverting and a noninverting input and an output, said noninverting input being maintained at a reference ground potential and said output being connected to said first opErational amplifier noninverting input, a fifth resistor connecting said output of said first operational amplifier to said inverting input of said fourth operational amplifier, a sixth resistor connecting said output of said fourth operational amplifier to its inverting input, and a seventh resistor coupling said output of said fourth operational amplifier to said inverting input of said second operational amplifier, said fourth through said seventh resistors having such values that a product of the resistance values for said fourth and sixth resistors is approximately equal to a product of the resistance values for said fifth and seventh resistors to effect enhanced voltage compliance across said load impedance.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |