Patent US2812381A successfully refreshed from Google Patents.
Patent US3745376A successfully refreshed from Google Patents.
US3745376A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency selective circuit including a twin-t notch filter
Assignee: TEL TONE CORP
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Filing: 1972-04-28
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Granted: 1973-07-10
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Expires: 1992-04-28
Abstract
Abstract A highly frequency selective circuit that includes a twin-T notch filter connected in the feedback path of a transistor is disclosed. Also included in the feedback path is an isolation network formed of a pair of emitter coupled transistors. One of the isolation transistors is fed by the feedback signal from the twin-T notch filter and the other is fed by the input signal to the overall frequency selective circuit.
Inventors
- 👤 A Mcintosh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 12:48
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1295; H04; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/444; H04Q1/45; H04Q1/453
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
71 words
A frequency selective circuit Comprising: an active electronic device having an input and an output; a twin-T notch filter having an input connected to the output of said active electronic device; and first and second emitter coupled transistors, the base of said first transistor being connected to the input of said active electronic device and the base of said second transistor being connected to the output of said twin-T notch filter.
Claim 2
Dependent Claim
71 words
A frequency selective circuit Comprising: an active electronic device having an input and an output; a twin-T notch filter having an input connected to the output of said active electronic device; and first and second emitter coupled transistors, the base of said first transistor being connected to the input of said active electronic device and the base of said second transistor being connected to the output of said twin-T notch filter.
Claim 3
Dependent Claim
30 words
A frequency selective circuit as claimed in claim 1 wherein said active electronic device includes a third transistor having a collector serving as the output of said active electronic device.
Claim 4
Dependent Claim
32 words
A frequency selective circuit as claimed in claim 2 wherein the collector of said third transistor is coupled to ground and wherein the collector of said second transistor is connected to ground.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |