US4085380A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Biquad RC active filter
Assignee: Boeing North American Inc
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Filing: 1976-11-26
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Granted: 1978-04-18
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Expires: 1996-11-26
Abstract
Abstract An RC active filter affords great flexibility for realizing biquadratic transfer functions, albeit with an extremely simple design comprising two operational amplifiers having plural inputs and outputs.
Inventors
- 👤 Jerry G. Williford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:35
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/34; H03F1/342; H03F1/36
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
129 words
A biquad RC active filter, comprising: a pair of operational amplifiers, each having an inverting and non-inverting input; a pair of capacitors, each being connected between the output and inverting input of a different one of said amplifiers; a first resistor connected to the inverting input of a first one of said amplifiers; a second resistor interconnecting the output of said first amplifier with the inverting input of the second one of said amplifiers; feedback circuit means interconnecting the output of said second amplifier with the non-inverting input of said first amplifier; a common terminal, and input circuit means for applying a signal referenced to said common terminal to at least one of the inputs of said amplifiers with the exception of the non-inverting input of said first amplifier.
Claim 2
Dependent Claim
129 words
A biquad RC active filter, comprising: a pair of operational amplifiers, each having an inverting and non-inverting input; a pair of capacitors, each being connected between the output and inverting input of a different one of said amplifiers; a first resistor connected to the inverting input of a first one of said amplifiers; a second resistor interconnecting the output of said first amplifier with the inverting input of the second one of said amplifiers; feedback circuit means interconnecting the output of said second amplifier with the non-inverting input of said first amplifier; a common terminal, and input circuit means for applying a signal referenced to said common terminal to at least one of the inputs of said amplifiers with the exception of the non-inverting input of said first amplifier.
Claim 3
Dependent Claim
25 words
The filter of claim 1 wherein said input circuit means comprises a resistor in the signal path to the inverting input of said second amplifier.
Claim 4
Dependent Claim
30 words
The filter of claim 1 wherein said input circuit means comprises means for individually altering the amplitude of the signal that is applied to the individual inputs of said amplifiers.
Claim 5
Dependent Claim
30 words
The filter of claim 1 wherein said feedback circuit means is a resistor and further including a resistor interconnecting the non-inverting input of said first amplifier with said common terminal.
Claim 6
Dependent Claim
31 words
The filter of claim 2 wherein said input circuit means applies the signal either to both inputs of said second amplifier simultaneously or to the input of said first amplifier exclusively.
Claim 7
Dependent Claim
25 words
The filter of claim 1 wherein the signal is applied exclusively to and the output signal is derived from the output of said first amplifier.
Claim 8
Dependent Claim
28 words
The filter of claim 1 wherein the signal is applied exclusively to said first amplifier and the output signal is derived from the output of said second amplifier.
Claim 9
Dependent Claim
14 words
The filter of claim 7 wherein said feedback circuit means is a short circuit.
Claim 10
Dependent Claim
30 words
The filter of claim 1 wherein the signal is applied to all three inputs of said amplifiers and the output signal is derived from the output of said first amplifier.
Claim 11
Dependent Claim
33 words
The filter of claim 1 wherein the signal is applied to the inverting inputs of both of said amplifiers and is attenuated before being applied to the non-inverting input of said second amplifier.
Claim 12
Dependent Claim
18 words
The filter of claim 1 wherein the output signal is derived from the output of said first amplifier.
Claim 13
Dependent Claim
18 words
The filter of claim 10 wherein the output signal is derived from the output of said second amplifier.
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) | 1981-04-17 | 1981-10-17 | 1982-04-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-17 | 1985-10-17 | 1986-04-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-17 | 1989-10-17 | 1990-04-18 | $7700.00 | Window Closed / Lapsed |