US4156853A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active filter for providing improved notch and band pass filters
Assignee: Westinghouse Electric Corp
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Filing: 1978-02-09
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Granted: 1979-05-29
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Expires: 1998-02-09
Abstract
Abstract An active filter is disclosed for providing improved notch and band pass filters. The output to input frequency response of an active filter is mathematically expressed as a ratio of two polynominals in the Laplace operator S. In any notch filter, the coefficient of the S term in the numerator must be reduced to zero, while in any band pass arrangement the coefficient of the S term in the denominator is reduced to zero. The improved notch filter provides an input circuit for the operational amplifier portion of the filter which eliminates the S term in the numerator so that adjustments to reduce this term are unnecessary. Similarly, in the improved band pass filter, the S term in the denominator is eliminated in the feedback circuit provided for the operational amplifier, so that adjustment is unnecessary to eliminate the coefficient of S.
Inventors
- 👤 Robert S. Peterson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:50
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
365 words
An active filter comprising: an operational amplifier (10) having an input, and an output for delivering a signal V o ; input circuit means for the operational amplifier (10) comprising, a first potentiometer (16), capacitors C 1 (24) and C 2 (26) resistors R 1 (28) and R 2 (30), and first impedance isolation means (12), the first potentiometer (16) being connected to a signal source V 1 , and having a wiper for selecting a voltage portion α 1 , the wiper being connected to the capacitor C 1 (24), said capacitor C 1 (24) being connected in parallel with resistor R 1 (28), the capacitor C 2 (26) being connected to said input, the first impedance isolation means (12) being interposed between the parallel combination C 1 R 1 (24, 28) and the capacitor C 2 (26), the resistor R 2 (30) being connected between the signal source V I and said input; feedback circuit means for the operational amplifier (10) comprising second (18) and third (20) potentiometers, capacitors C 3 (32), C 4 (34) and C 5 (36), second impedance isolation means (14) and resistors R 3 (38) and R 4 (40), the second potentiometer (18) being connected to said output and having a wiper for selecting a voltage portion α 2 , the wiper being connected to said capacitor C 3 (32) which is connected in parallel with resistor R 3 (38), the capacitor C 4 (34) being connected to said input, the second impedance isolation means (14) being interposed between the capacitor C 4 (34) and the parallel combination of resistor R 3 (38) and capacitor C 3 (32), the third potentiometer (20) having a wiper for selecting a voltage portion β, the wiper being connected to said input through capacitor C 5 (36), the resistor R 4 (40) being connected between said output and said input, the components having equal magnitudes C 1 =C 3 ; C 2 =C 4 ; R 1 =R 3 ; R 2 =R 4 , the time constants C 2 R 1 =C 1 R 2 =C x R x , and α 1 =α 2 =α to provide the transfer function: ##EQU17##
Claim 2
Dependent Claim
365 words
An active filter comprising: an operational amplifier (10) having an input, and an output for delivering a signal V o ; input circuit means for the operational amplifier (10) comprising, a first potentiometer (16), capacitors C 1 (24) and C 2 (26) resistors R 1 (28) and R 2 (30), and first impedance isolation means (12), the first potentiometer (16) being connected to a signal source V 1 , and having a wiper for selecting a voltage portion α 1 , the wiper being connected to the capacitor C 1 (24), said capacitor C 1 (24) being connected in parallel with resistor R 1 (28), the capacitor C 2 (26) being connected to said input, the first impedance isolation means (12) being interposed between the parallel combination C 1 R 1 (24, 28) and the capacitor C 2 (26), the resistor R 2 (30) being connected between the signal source V I and said input; feedback circuit means for the operational amplifier (10) comprising second (18) and third (20) potentiometers, capacitors C 3 (32), C 4 (34) and C 5 (36), second impedance isolation means (14) and resistors R 3 (38) and R 4 (40), the second potentiometer (18) being connected to said output and having a wiper for selecting a voltage portion α 2 , the wiper being connected to said capacitor C 3 (32) which is connected in parallel with resistor R 3 (38), the capacitor C 4 (34) being connected to said input, the second impedance isolation means (14) being interposed between the capacitor C 4 (34) and the parallel combination of resistor R 3 (38) and capacitor C 3 (32), the third potentiometer (20) having a wiper for selecting a voltage portion β, the wiper being connected to said input through capacitor C 5 (36), the resistor R 4 (40) being connected between said output and said input, the components having equal magnitudes C 1 =C 3 ; C 2 =C 4 ; R 1 =R 3 ; R 2 =R 4 , the time constants C 2 R 1 =C 1 R 2 =C x R x , and α 1 =α 2 =α to provide the transfer function: ##EQU17##
Claim 3
Dependent Claim
20 words
An active filter according to claim 1 wherein said first (12) and second (14) impedance isolation means are emitter followers.
Claim 4
Dependent Claim
347 words
An active filter comprising: an operational amplifier (10) having an input, and an output for delivering a signal V o ; input circuit means for the operational amplifier (10) comprising first (16) and second (22) potentiometers, capacitors C 1 C 2 (24, 26) and C 3 (42), resistors R 1 (28) and R 2 (30), and first impedance isolation means (12), said first potentiometer (16) being connected to a signal source V I , having a wiper for selecting a voltage portion α 1 and being connected to the capacitor C 1 (24), said capacitor C 1 (24) being connected in parallel with resistor R 1 (28), the capacitor C 2 (26) being connected to said input, the first impedance isolation means (12) being interposed between the parallel combination R 1 C 1 (28, 24) and the capacitor C 2 (26), the resistor R 2 (30) being connected between the signal source V I and said input, the second potentiometer (22) being connected to the voltage source V I , having a wiper for selecting a voltage portion β and being connected to said input through the capacitor C 3 (42), feedback circuit means for the operational amplifier comprising a third potentiometer (18), capacitors C 4 (32) and C 5 (34) and resistors R 3 (38) and R 4 (40), the third potentiometer (18) being connected to said output, having a wiper for selecting a voltage portion α 2 , said wiper being connected to said capacitor C 4 (32) which is connected in parallel with resistor R 3 (38), the capacitor C 5 (34) being connected to said input, the second impedance isolation means (14) being interposed between capacitor C 5 (32) and the parallel combination R 3 C 4 (38, 32), the resistor R 4 (40) being connected between said output and said input, the components having equal magnitude C 1 =C 4 ; C 2 =C 5 =C x R x ; R 1 =R 3 ; R 2 =R 4 , and α 1 =α 2 =α to provide the transfer function: ##EQU18##
Claim 5
Dependent Claim
347 words
An active filter comprising: an operational amplifier (10) having an input, and an output for delivering a signal V o ; input circuit means for the operational amplifier (10) comprising first (16) and second (22) potentiometers, capacitors C 1 C 2 (24, 26) and C 3 (42), resistors R 1 (28) and R 2 (30), and first impedance isolation means (12), said first potentiometer (16) being connected to a signal source V I , having a wiper for selecting a voltage portion α 1 and being connected to the capacitor C 1 (24), said capacitor C 1 (24) being connected in parallel with resistor R 1 (28), the capacitor C 2 (26) being connected to said input, the first impedance isolation means (12) being interposed between the parallel combination R 1 C 1 (28, 24) and the capacitor C 2 (26), the resistor R 2 (30) being connected between the signal source V I and said input, the second potentiometer (22) being connected to the voltage source V I , having a wiper for selecting a voltage portion β and being connected to said input through the capacitor C 3 (42), feedback circuit means for the operational amplifier comprising a third potentiometer (18), capacitors C 4 (32) and C 5 (34) and resistors R 3 (38) and R 4 (40), the third potentiometer (18) being connected to said output, having a wiper for selecting a voltage portion α 2 , said wiper being connected to said capacitor C 4 (32) which is connected in parallel with resistor R 3 (38), the capacitor C 5 (34) being connected to said input, the second impedance isolation means (14) being interposed between capacitor C 5 (32) and the parallel combination R 3 C 4 (38, 32), the resistor R 4 (40) being connected between said output and said input, the components having equal magnitude C 1 =C 4 ; C 2 =C 5 =C x R x ; R 1 =R 3 ; R 2 =R 4 , and α 1 =α 2 =α to provide the transfer function: ##EQU18##
Claim 6
Dependent Claim
20 words
An active filter according to claim 3 wherein the first (12) and second (14) impedance isolation means are emitter followers.
References Cited (Backward Citations)
US3356962A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-05-28 | 1982-11-27 | 1983-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-28 | 1986-11-27 | 1987-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-28 | 1990-11-27 | 1991-05-29 | $7700.00 | Window Closed / Lapsed |