Patent US3778725A successfully refreshed from Google Patents.
US3778725A
Expired / Lapsed
US
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Non-drifting hold-amplifier
Assignee: Shell USA Inc
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Filing: 1972-07-06
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Granted: 1973-12-11
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Expires: 1992-07-06
Abstract
Abstract A method and apparatus for controlling a process wherein a hold amplifier is used to maintain the charge on a capacitor, the charge on the capacitor representing the desired position of a control element. The charge on the capacitor is maintained by periodically connecting it to a reference voltage.
Inventors
- 👤 K Spaargaren
- 👤 J Snoeks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:37
CPC Classifications
G; G11; G11C; G11C27/00; G11C27/02; G11C27/024; G11C27/026; G05; G05B; G05B1/00; G05B1/01; G05B1/02; G11C11/00; G11C11/21; G11C11/34; G11C11/40; G11C11/401; G11C11/403; G11C11/56; G11C11/565; G11C7/00; G11C7/06
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
141 words
An apparatus for maintaining a voltage present on a capacitor comprising: a first differential amplifier, the output of which is fed back into one of the two inputs of said first differential amplifier; a storage capacitor connected to the other input of the said differential amplifier; a reference voltage source capable of supplying a voltage which varies with time along a number of discrete levels; a second differential amplifier one input of which is connected to the output of the first differential amplifier and the other input to the reference voltage source; a switch element permitting the passage of current - in two directions and capable of connecting the reference voltage source to the storage capacitor; a threshold value detector connected to the output of the second differential amplifier, the output of the said detector being connected to the switch element.
Claim 2
Independent Claim
141 words
An apparatus for maintaining a voltage present on a capacitor comprising: a first differential amplifier, the output of which is fed back into one of the two inputs of said first differential amplifier; a storage capacitor connected to the other input of the said differential amplifier; a reference voltage source capable of supplying a voltage which varies with time along a number of discrete levels; a second differential amplifier one input of which is connected to the output of the first differential amplifier and the other input to the reference voltage source; a switch element permitting the passage of current - in two directions and capable of connecting the reference voltage source to the storage capacitor; a threshold value detector connected to the output of the second differential amplifier, the output of the said detector being connected to the switch element.
Claim 3
Dependent Claim
35 words
An apparatus as claimed in claim 1, characterized in that the threshold value detector is formed by a Schmitt trigger followed by a pulse generator which is capable of transmitting pulses to the switch element.
Claim 4
Dependent Claim
26 words
An apparatus as claimed in claim 2, characterized in that the length and shape of the pulses from the pulse generator can be preset and controlled.
References Cited (Backward Citations)
US3390381A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |