US3602833A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active twin t filter with a positive feedback q control
Assignee: United States Department of the Navy
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Filing: 1969-09-23
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Granted: 1971-08-31
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Expires: 1989-09-23
Abstract
Abstract An active twin T filter in which current is drawn from an amplifier or from the legs of a twin T network and passed as feedback to the positive input side of the amplifier to provide Q control and the combination thereof with the passage of feedback current from the network to the negative input of the amplifier to provide frequency control, both controls being obtained without need to vary the passive resistor and capacitor elements of the circuit.
Inventors
- 👤 William E Barnette
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:56
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1295
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
164 words
An active twin T filter circuit comprising: a differential amplifier having an output connection and positive and negative input connections; means for applying input signals to said negative input connection; a twin T network comprising a first T network including a capacitor as a center leg leading from between two series connected resistors, a second T network including a resistor as a center leg leading from between two series connected capacitors, said center legs being connected to form a junction therebetween, and resistive means connecting said junction to ground; means for connecting said series-connected capacitors in parallel with said series-connected resistors between said output connection of said differential amplifier and said negative input connection thereof; and said resistive means comprising a potentiometer having its wiper connected to said positive input connection whereby a positive feedback signal is derived from the current in said legs, which signal can be selectively varied by adjustment of said wiper without affecting the balance of said twin T network.
Claim 2
Dependent Claim
164 words
An active twin T filter circuit comprising: a differential amplifier having an output connection and positive and negative input connections; means for applying input signals to said negative input connection; a twin T network comprising a first T network including a capacitor as a center leg leading from between two series connected resistors, a second T network including a resistor as a center leg leading from between two series connected capacitors, said center legs being connected to form a junction therebetween, and resistive means connecting said junction to ground; means for connecting said series-connected capacitors in parallel with said series-connected resistors between said output connection of said differential amplifier and said negative input connection thereof; and said resistive means comprising a potentiometer having its wiper connected to said positive input connection whereby a positive feedback signal is derived from the current in said legs, which signal can be selectively varied by adjustment of said wiper without affecting the balance of said twin T network.
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) | 1974-08-30 | 1975-03-01 | 1975-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-30 | 1979-03-01 | 1979-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-30 | 1983-03-01 | 1983-08-31 | $7700.00 | Window Closed / Lapsed |