US3701037A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active filter
Assignee: Infinet Inc
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Filing: 1971-06-24
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Granted: 1972-10-24
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Expires: 1991-06-24
Abstract
Abstract An active filter circuit. Two cascaded phase shift networks are in circuit with the non-inverting input terminal of an operational amplifier. A resistive feedback network couples the amplifier output back to the first of the phase shift networks. When an external input signal is applied to both phase shift networks and the inverting input terminal of the amplifier, the filter circuit has a pass band and a stop band. Inputs to any single one of these points selectably provide high-pass, low-pass and band-pass operation.
Inventors
- 👤 Jerry L Holsinger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:21
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
80 words
A filter for connection between a signal source and a utilization circuit, said filter comprising: A. a first phase shift network, B. a second phase-shift network energized by the first phase shift network, C. a summing network energized by the second phase shift network, the output from said summing circuit being coupled to the input of said first phase shift network, D. means for connecting the signal source to said first and second phase shift networks and said summing circuit.
Claim 2
Dependent Claim
80 words
A filter for connection between a signal source and a utilization circuit, said filter comprising: A. a first phase shift network, B. a second phase-shift network energized by the first phase shift network, C. a summing network energized by the second phase shift network, the output from said summing circuit being coupled to the input of said first phase shift network, D. means for connecting the signal source to said first and second phase shift networks and said summing circuit.
Claim 3
Dependent Claim
16 words
A filter as recited in claim 1 wherein said first phase shift network is an integrator.
Claim 4
Dependent Claim
17 words
A filter as recited in claim 1 wherein said second phase shift network is a lag network.
Claim 5
Dependent Claim
44 words
A filter as recited in claim 1 wherein said summing network comprises an operational amplifier with first and second input terminals, said first input terminal being connected to said connecting means and said second input terminal being connected to said second phase shift network.
Claim 6
Dependent Claim
88 words
A filter as recited in claim 1: A. wherein said first phase shift network is an integrator, B. wherein said second phase shift network imparts a phase shift in a direction generally opposite to that of said integrator, C. including feedback means between the output of said filter and the input of said first phase shift network, and D. wherein said connecting means connects the signal source to said phase shift networks and said summing circuit simultaneously thereby to provide the filter with both pole and notch characteristics.
Claim 7
Dependent Claim
134 words
A filter with a stop band and a pass band for connection between a signal source and utilization circuit, said filter comprising: A. first and second operational amplifiers, B. capacitive negative feedback means for said first operational amplifier, C. a first resistor coupling the input terminal of said first operation amplifier to the signal source, D. a lag network energized by said first operational amplifier, the output of said lag network being coupled to a first, non-inverting input terminal of the second operational amplifier, E. means coupling the signal source to the lag network, F. a third resistor coupling the source to an inverting second input of said second operational amplifier, and G. a fourth resistor connected between the output of said second operational amplifier and the input terminal of the first operational amplifier.
Claim 8
Dependent Claim
134 words
A filter with a stop band and a pass band for connection between a signal source and utilization circuit, said filter comprising: A. first and second operational amplifiers, B. capacitive negative feedback means for said first operational amplifier, C. a first resistor coupling the input terminal of said first operation amplifier to the signal source, D. a lag network energized by said first operational amplifier, the output of said lag network being coupled to a first, non-inverting input terminal of the second operational amplifier, E. means coupling the signal source to the lag network, F. a third resistor coupling the source to an inverting second input of said second operational amplifier, and G. a fourth resistor connected between the output of said second operational amplifier and the input terminal of the first operational amplifier.
Claim 9
Dependent Claim
38 words
A filter circuit as recited in claim 6 wherein: A. said lag network comprises a fifth resistor and a second capacitor, and B. said coupling means comprises a sixth resistor connected between said source and said second capacitor.
References Cited (Backward Citations)
US2831975A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-24 | 1976-04-24 | 1976-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-24 | 1980-04-24 | 1980-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-24 | 1984-04-24 | 1984-10-24 | $7700.00 | Window Closed / Lapsed |