US3831103A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active filter circuit
Assignee: Beckman Coulter Inc
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Filing: 1973-04-30
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Granted: 1974-08-20
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Expires: 1993-04-30
Abstract
Abstract An active element sharp cut-off bandpass filter circuit having independently tunable center frequency and Q characteristics. The filter circuit incorporates a high performance operational amplifier having one input connected to ground and a pair of feedback paths interconnecting the amplifier output and the other input. One feedback path includes two capacitors connected in series and the other path includes two resistors connected in series. The input to the filter circuit is connected, via an input resistor, to the common juncture of the capacitors; and the amplifier output is connected to the filter output terminal, as well as to one end of a grounded voltage divider having a movable tap. The common juncture of the feedback resistors is connected, via a capacitor, to the movable tap of the voltage divider. In one embodiment the capacitors have equal values and the feedback resistors have values which are four times the value of the input resistor.
Inventors
- 👤 F Ruegg
- 👤 L Silva
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:57
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1295
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
183 words
A sharp cut-off bandpass filter circuit comprising a high performance amplifier having an inverting input terminal, a grounded noninverting input terminal, and an output terminal which serves as the output of the filter circuit; first feedback circuit means including two series connected capacitors electrically interconnecting the amplifier output terminal and the inverting input terminal; second feedback circuit means including two series connected resistors interconnecting the amplifier output terminal and the noninverting input terminal; a variable input resistor connected between a filter input terminal and the common juncture of said capacitors; an adjustable voltage divider having a movable center tap, one end of said voltage divider being connected to the amplifier output terminal and the other end of said divider being connected to ground; a capacitor electrically connected between the common juncture of said resistors and said movable tap of the voltage divider whereby the center frequency of the filter circuit is tunable by adjusting the value of the input resistor and the Q characteristic of the filter is tunable, independently of the center frequency, by varying the movable tap of the divider resistor.
Claim 2
Dependent Claim
183 words
A sharp cut-off bandpass filter circuit comprising a high performance amplifier having an inverting input terminal, a grounded noninverting input terminal, and an output terminal which serves as the output of the filter circuit; first feedback circuit means including two series connected capacitors electrically interconnecting the amplifier output terminal and the inverting input terminal; second feedback circuit means including two series connected resistors interconnecting the amplifier output terminal and the noninverting input terminal; a variable input resistor connected between a filter input terminal and the common juncture of said capacitors; an adjustable voltage divider having a movable center tap, one end of said voltage divider being connected to the amplifier output terminal and the other end of said divider being connected to ground; a capacitor electrically connected between the common juncture of said resistors and said movable tap of the voltage divider whereby the center frequency of the filter circuit is tunable by adjusting the value of the input resistor and the Q characteristic of the filter is tunable, independently of the center frequency, by varying the movable tap of the divider resistor.
Claim 3
Dependent Claim
41 words
The sharp cut-off filter of claim 1 wherein the capacitor in the first feedback circuit means are of equal value and the resistors in the second feedback circuit means are each of about four times the magnitude of the input resistor.
Claim 4
Dependent Claim
29 words
A sharp cut-off filter circuit as described in claim 1 including multiple stages, with the output of each stage being connected to the input of the next succeeding stage.
Claim 5
Dependent Claim
171 words
A sharp cut-off band pass filter circuit comprising a high performance amplifier means having at least one input and an output; capacitive feedback means electrically interconnecting the output of said amplifier means and an input thereof; said capacitive feedback means comprising two capacitors of equal value connected in series in the feedback path; resistive feedback means electrically interconnecting the output of said amplifier means and said input thereof, said resistive feedback means comprising two resistors of equal value connected in series in said feedback path; means connected to said capacitive feedback means for adjusting the center frequency of said filteR circuit, and means connected to the resitive feedback means for independently adjusting the Q characteristic of the filter circuit, independently of the center frequency, said means for adjusting the Q characteristic comprising a divider resistor having a movable center tap, said divider resistor being connected between the output of said amplifier means and ground, with the center tap electrically connected to the common juncture of said feedback resistors through a capacitor.
Claim 6
Dependent Claim
171 words
A sharp cut-off band pass filter circuit comprising a high performance amplifier means having at least one input and an output; capacitive feedback means electrically interconnecting the output of said amplifier means and an input thereof; said capacitive feedback means comprising two capacitors of equal value connected in series in the feedback path; resistive feedback means electrically interconnecting the output of said amplifier means and said input thereof, said resistive feedback means comprising two resistors of equal value connected in series in said feedback path; means connected to said capacitive feedback means for adjusting the center frequency of said filteR circuit, and means connected to the resitive feedback means for independently adjusting the Q characteristic of the filter circuit, independently of the center frequency, said means for adjusting the Q characteristic comprising a divider resistor having a movable center tap, said divider resistor being connected between the output of said amplifier means and ground, with the center tap electrically connected to the common juncture of said feedback resistors through a capacitor.
Claim 7
Dependent Claim
48 words
The filter circuit of claim 4 wherein said means for adjusting the center frequency of said filter circuit includes an adjustable input resistor connected to the common juncture of said capacitors, said resistors in said feedback circuit being of about four times the magnitude of said input resistor.
References Cited (Backward Citations)
US2924782A
Cited
US3622833A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-19 | 1978-02-18 | 1978-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-19 | 1982-02-18 | 1982-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-19 | 1986-02-18 | 1986-08-20 | $7700.00 | Window Closed / Lapsed |