Patent US3863173A successfully refreshed from Google Patents.
US3863173A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Amplifier circuit for minimizing voltage offset
Assignee: General Electric Co
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Filing: 1974-06-03
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Granted: 1975-01-28
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Expires: 1994-06-03
Abstract
Abstract An improved low-pass multistage active filter circuit manufactured from monolithic and hybrid circuits is provided having a plurality of cascaded amplifier stages coupled to one another through filter sections and having an external DC negative feedback loop comprising a feedback resistor connected between the output of the lastcascaded amplifier and inverting input of the first of the cascaded amplifiers, and which feedback resistor substantially matches in resistance value the D.C. component value of an input impedance for the filter. The feedback circuit acts to eliminate a contribution to a voltage offset at each amplifier stage by nullifying, reducing or canceling an inherent voltage offset produced by each operational amplifier stage except the first operational amplifier stage.
Inventors
- 👤 Paul E Scheib
- 👤 Robert H Shumate
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 07:28
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/34; H03F3/343; H03F3/347; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
201 words
In a filter circuit including in combination, a plurality of cascaded amplifier stages coupled to one another through filter elements and exhibiting a unity voltage gain over each stage, the first of said amplifier stages having first and second input terminals and an output terminal, the last of said amplifiers having an output terminal, a filter circuit input, and an input impedance connected in series between said first terminal and said filter circuit input, the improvement comprising: a first negative feedback circuit comprising a first feedback impedance connected between said output terminal of said last amplifier and said second input terminal, a second negative feedback circuit comprising a second feedback impedance connected between said second input terminal of said first amplifier and said output terminal of said first amplifier, said second feedback impedance being dimensioned such that at and above the cut-off frequency of the filter circuit its impedance value is substantially lower than that of said first feedback impedance, whereas for direct current its impedance value is substantially higher than that of said first feedback impedance and said first feedback impedance being dimensioned such that for direct current its impedance value is substantially equal to that of said input impedance.
Claim 2
Dependent Claim
201 words
In a filter circuit including in combination, a plurality of cascaded amplifier stages coupled to one another through filter elements and exhibiting a unity voltage gain over each stage, the first of said amplifier stages having first and second input terminals and an output terminal, the last of said amplifiers having an output terminal, a filter circuit input, and an input impedance connected in series between said first terminal and said filter circuit input, the improvement comprising: a first negative feedback circuit comprising a first feedback impedance connected between said output terminal of said last amplifier and said second input terminal, a second negative feedback circuit comprising a second feedback impedance connected between said second input terminal of said first amplifier and said output terminal of said first amplifier, said second feedback impedance being dimensioned such that at and above the cut-off frequency of the filter circuit its impedance value is substantially lower than that of said first feedback impedance, whereas for direct current its impedance value is substantially higher than that of said first feedback impedance and said first feedback impedance being dimensioned such that for direct current its impedance value is substantially equal to that of said input impedance.
Claim 3
Dependent Claim
16 words
A filter circuit as defined in claim 1 wherein said first feedback impedance is a resistance.
Claim 4
Dependent Claim
16 words
A filter circuit as defined in claim 2 wherein said second feedback impedance is a capacitance.
Claim 5
Dependent Claim
14 words
A filter circuit as defined in claim 3 wherein said amplifiers are operational amplifiers.
Claim 6
Dependent Claim
15 words
A filter circuit as defined in claim 4 wherein said input impedance is a resistance.
Claim 7
Dependent Claim
28 words
A filter circuit as defined in claim 5 wherein each of said filter elements comprise a passive filter network serially connected between each pair of successive amplifier stages.
Claim 8
Dependent Claim
39 words
A filter circuit as defined in claim 1 wherein said first impedance is a resistance, said second impedance a capacitance, said input impedance a resistance, said amplifiers being operational amplifiers and said filter elements each comprising a resistance-capacitance network.
References Cited (Backward Citations)
US3707685A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-01-27 | 1978-07-29 | 1979-01-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-01-27 | 1982-07-29 | 1983-01-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-01-27 | 1986-07-29 | 1987-01-28 | $7700.00 | Window Closed / Lapsed |