US3801919A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Null loop for correcting low frequency error signals in high performance amplifiers
Assignee: MANDREL IND INC US
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Filing: 1972-10-30
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Granted: 1974-04-02
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Expires: 1992-10-30
Abstract
Abstract A feedback null loop includes a low drift, first loop amplifier connected to the output of a fast settling, large drift amplifier means which is to be corrected for AC and DC errors due to stray signal coupling. A second loop amplifier with high impedance is coupled to the low drift first loop amplifier via electronic switch means. A ground line is provided to the input of the large drift amplifier means; e.g., via the conventional multiplexer apparatus in a multi-channel data acquisition system, whereby the output voltage of the amplifier means is nulled to zero. Prior to opening the switch means in the null loop, a capacitor stores a fixed voltage representing the error signal. Thereafter, as the multiplexer apparatus selects successive channels of the data acquisition system, any DC off-set levels are balanced out via the temporarily stored capacitor voltage.
Inventors
- 👤 D Wilkes
- 👤 C Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:19
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/30; H03F1/303; H03F2200/00; H03F2200/372
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
111 words
An amplifier null loop for reducing DC and low frequency AC offset and drift in wideband, fast settling, high performance operational amplifiers with high drift characteristics, comprising the combination of: means for selectively grounding the input of the wideband, fast settling, high performance operational amplifier; and a feedback loop including: a low drift, chopper-stabilized, operational amplifier; a high input impedance operational amplifier; a storage capacitor coupled across the high input impedance amplifier for storing a fixed voltage representing the output of the high performance amplifier when the input thereto is grounded; and a switch for selectively coupling the feedback loop from the output to the input of the high performance amplifier.
Claim 2
Dependent Claim
111 words
An amplifier null loop for reducing DC and low frequency AC offset and drift in wideband, fast settling, high performance operational amplifiers with high drift characteristics, comprising the combination of: means for selectively grounding the input of the wideband, fast settling, high performance operational amplifier; and a feedback loop including: a low drift, chopper-stabilized, operational amplifier; a high input impedance operational amplifier; a storage capacitor coupled across the high input impedance amplifier for storing a fixed voltage representing the output of the high performance amplifier when the input thereto is grounded; and a switch for selectively coupling the feedback loop from the output to the input of the high performance amplifier.
Claim 3
Dependent Claim
56 words
The amplifier null loop of claim 1, wherein the low drift operational amplifier is coupled to the output of the high performance amplifier, the switch is coupled to the output of the low drift operational amplifier, and the high input impedance operational amplifier is coupled between said switch and the input to said high performance amplifier.
Claim 4
Dependent Claim
52 words
The amplifier null loop of claim 1, wherein the means for selectively grounding the input of the high performance amplifier includes a multiplexer for periodically connecting each of a set of successive input data channels to said input and at least one of the input data channels of said set represents ground.
Claim 5
Dependent Claim
28 words
The amplifier null loop of claim 3, wherein the first input data channel of said set represents ground and said set comprises at least four input data channels.
Claim 6
Dependent Claim
42 words
The amplifier null loop of claim 3, wherein the input impedance of the high input impedance amplifier is sufficient to hold the fixed voltage on the storage capacitor for the time between successive groundings of the input of the high performance amplifier.
References Cited (Backward Citations)
US3667055A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |