US3569848A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Unconditionally stable, open loop operational amplifier
Assignee: International Business Machines Corp
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Filing: 1968-12-12
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Granted: 1971-03-09
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Expires: 1988-12-12
Abstract
Abstract An open loop semiconductor operational amplifier having a differential amplifying input stage, an output stage having high input and low output impedance, and an intermediate stage interconnecting the input and output stage and having low input impedance and high output impedance. The three stages are collectively responsive to an applied input signal so as to maintain unconditional stability up to unity gain operation without external feedback circuitry.
Inventors
- 👤 Daniel J Esteban
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:42
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/08; H03F1/083; H03F3/00; H03F3/30; H03F3/3083; H03F3/3086; H03F3/3091; H03F3/45; H03F3/45071
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
360 words
An open-loop operational amplifier for amplifying an applied input signal, adaptable for circuit integration, and having unconditional stability of operation without external feedback circuitry means comprising: a. a pair of input terminals for receiving an input signal; b. a differential amplifier input stage including first and second transistors, each base terminal of the first and second transistors being connected to a respective one of the pair of input terminals; c. a first source of constant current, each emitter of the first and second transistors being connected in common and to the first source of constant current; d. a second stage comprising a grounded base transistor amplifier means having first, second, and third terminals, and an output node connected to the second terminal, the first terminal being adapted to receive an input signal from the collector of the second transistor, the second terminal being connected to a second source of constant current, and the third terminal being connected to a first biasing network for providing a grounded base mode of operation; e. the collector of the first transistor being connected to a second biasing network for providing collector current thereto, f. an emitter follower output stage, the emitter follower output stage being adapted to receive an input signal from the output node of the grounded base transistor amplifier means so as to provide an output voltage from the open-loop operational amplifier; and g. a temperature compensated constant current source for stabilizing the output voltage generated at the output node of the grounded base transistor ampliFier means, the temperature compensated constant current source being connected between collector terminal of the first transistor and the second constant current source and being responsive to a change in the collector current to the first transistor for supplying a current to the second constant current source so as to offset the change in collector current to the second transistor in order to prevent the change in collector current to the second transistor from varying the DC output voltage at the output node of the grounded base transistor amplifier means due to ambient temperature changes and to DC voltage fluctuations at the first and second biasing networks.
Claim 2
Dependent Claim
360 words
An open-loop operational amplifier for amplifying an applied input signal, adaptable for circuit integration, and having unconditional stability of operation without external feedback circuitry means comprising: a. a pair of input terminals for receiving an input signal; b. a differential amplifier input stage including first and second transistors, each base terminal of the first and second transistors being connected to a respective one of the pair of input terminals; c. a first source of constant current, each emitter of the first and second transistors being connected in common and to the first source of constant current; d. a second stage comprising a grounded base transistor amplifier means having first, second, and third terminals, and an output node connected to the second terminal, the first terminal being adapted to receive an input signal from the collector of the second transistor, the second terminal being connected to a second source of constant current, and the third terminal being connected to a first biasing network for providing a grounded base mode of operation; e. the collector of the first transistor being connected to a second biasing network for providing collector current thereto, f. an emitter follower output stage, the emitter follower output stage being adapted to receive an input signal from the output node of the grounded base transistor amplifier means so as to provide an output voltage from the open-loop operational amplifier; and g. a temperature compensated constant current source for stabilizing the output voltage generated at the output node of the grounded base transistor ampliFier means, the temperature compensated constant current source being connected between collector terminal of the first transistor and the second constant current source and being responsive to a change in the collector current to the first transistor for supplying a current to the second constant current source so as to offset the change in collector current to the second transistor in order to prevent the change in collector current to the second transistor from varying the DC output voltage at the output node of the grounded base transistor amplifier means due to ambient temperature changes and to DC voltage fluctuations at the first and second biasing networks.
Claim 3
Dependent Claim
96 words
An open-loop operational amplifier for amplifying an applied input signal, adaptable for circuit integration, and having unconditional stability of operation without external feedback circuitry means as in claim 1 wherein: a. the temperature compensated constant current source includes a third transistor connected to a third biasing network; and b. a semiconductor element connected to the collector of the first transistor and to the temperature compensated constant current source, the semiconductor element being responsive to the collector current of the first transistor for offsetting the base-emitter voltage change of the third transistor due to ambient temperature changes.
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) | 1974-03-08 | 1974-09-07 | 1975-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-08 | 1978-09-07 | 1979-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-08 | 1982-09-07 | 1983-03-09 | $7700.00 | Window Closed / Lapsed |