US4382233A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiple-feedback path filter
Assignee: St Clair Intellectual Property Consultants Inc
•
Filing: 1980-11-12
•
Granted: 1983-05-03
•
Expires: 2000-11-12
Abstract
Abstract A multiple-feedback path bandpass/bandreject filter which exhibits a nearly constant Q over a predetermined frequency range, and which is tunable by means of a single variable impedance element is provided. A Thevenin equivalent voltage source is placed in series with the tuning element, wherein the Thevenin voltage is a predetermined constant fractional amplitude of the bandreject output voltage, or its equivalent.
Inventors
- 👤 Bruce E. Hofer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 01:17
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1291
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
62 words
A multiple feedback path filter comprising in combination: an operational amplifier having a plurality of feedback paths from output to input, said feedback paths including one or more impedance elements; a single variable-impedance tuning element connected to said operational amplifier; and means for applying a voltage to said variable-impedance tuning element to effect a nearly constant Q over a predetermined frequency range.
Claim 2
Dependent Claim
62 words
A multiple feedback path filter comprising in combination: an operational amplifier having a plurality of feedback paths from output to input, said feedback paths including one or more impedance elements; a single variable-impedance tuning element connected to said operational amplifier; and means for applying a voltage to said variable-impedance tuning element to effect a nearly constant Q over a predetermined frequency range.
Claim 3
Dependent Claim
46 words
A filter in accordance with claim 1 wherein said filter is an active RC bandpass filter, and said voltage applying means comprises a Thevenin equivalent voltage source which is a predetermined combination of the input signal voltage and the bandpass output signal voltage of said filter.
Claim 4
Dependent Claim
24 words
A filter in accordance with claim 2 wherein said Thevenin equivalent voltage source comprises a voltage divider connected between the filter input and output.
Claim 5
Dependent Claim
40 words
A filter in accordance with claim 1 wherein said filter is an active RC bandpass/bandreject filter, and said voltage applying means comprises a Thevenin equivalent voltage source which is a predetermined constant fractional amplitude of the bandreject output signal voltage.
References Cited (Backward Citations)
US3743957A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-05-02 | 1986-11-01 | 1987-05-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-05-02 | 1990-11-01 | 1991-05-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-05-02 | 1994-11-01 | 1995-05-03 | $7700.00 | Window Closed / Lapsed |