US3706936A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Selectively switched multi purpose electrical filter
Assignee: KROHN HITE CORP
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Filing: 1970-10-28
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Granted: 1972-12-19
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Expires: 1990-10-28
Abstract
Abstract A universal electronic filter includes a high pass section with an adjustable high cutoff frequency, a low pass section with an adjustable low cutoff frequency and a switching arrangement for interconnecting the two sections to provide high pass operation, low pass operation, band pass or band reject operation, all with adjustable cutoff frequencies. The high pass section includes means for adjusting the gain on one output while keeping it constant on another and applying the output from the constant gain portion to a shunt section to peak at a corner frequency without the peak changing as the gain is adjusted. In the low pass section there is a PNP stage in cascade with an NPN stage with the same number of PNP''s as NPN''s to cancel d-c drift. In both low and high pass sections the degree of feedback is varied with change in slope. In the low pass section feedback to both collector and emitter with the feedback to the emitter through a capacitor helps keep the section operating at higher frequencies.
Inventors
- 👤 Earl H Krohn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 20:15
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
77 words
Electrical filtering apparatus having filter means with at least one adjustable cutoff frequency comprising, circuit means having feedback, means for adjusting said cutoff frequency, means for selectively adjusting the slope of the transmission characteristic of said filter means, and means for adjusting said feedback at the same time said slope is adjusted to reduce the feedback with decreasing slope so that the frequency of the 3 db down point does not change with changes in selected slope.
Claim 2
Dependent Claim
77 words
Electrical filtering apparatus having filter means with at least one adjustable cutoff frequency comprising, circuit means having feedback, means for adjusting said cutoff frequency, means for selectively adjusting the slope of the transmission characteristic of said filter means, and means for adjusting said feedback at the same time said slope is adjusted to reduce the feedback with decreasing slope so that the frequency of the 3 db down point does not change with changes in selected slope.
Claim 3
Dependent Claim
90 words
Filtering apparatus in accordance with claim 1 and further including a high pass section having circuit means characterized by a pair of outputs with means for keeping the gain on one of said outputs constant and adjusting the gain of the other, and means for combining the signal on the constant gain output with that on the variable gain output for peaking at a corner frequency near the edge of the transmission band so that the corner frequency does not change with changes in said variable gain or said slope.
Claim 4
Dependent Claim
40 words
Filtering apparatus in accordance with claim 1 and further including a low pass section including cascaded PNP and NPN stages with the same number of PNP as NPN devices for providing essentially zero d-c drift in said low pass section.
Claim 5
Dependent Claim
196 words
Filtering apparatus in accordance with claim 1 capable of low pass, high pass, band pass and band reject operation comprising, an input terminal, means defining input, intermediate and output junctions, an output terminal, a low pass section, a high pass section, means for continuously coupling the output of said high pass section to said output terminal, means including said intermediate junction for grounding the input of said high pass section when said filtering means is in the low pass mode, means including said input junction for coupling said input terminal to the input of said high pass section when in the high pass and band reject mode, means including said input junction for coupling said input terminal to said input of said low pass section when in said low pass, band pass and band reject mode, means including said output junction and said intermediate junction for coupling the output of said low pass section to the input of said high pass section when in said band pass mode, and means including said output junction for coupling the output of said low pass section to said output terminal when in the band reject and low pass mode.
Claim 6
Dependent Claim
26 words
Filtering apparatus in accordance with claim 4 and further comprising means for grounding the input of said low pass section when in said high pass mode.
Claim 7
Dependent Claim
40 words
Filtering apparatus in accordance with claim 2 and further including a low pass section including cascaded PNP and NPN stages with the same number of PNP as NPN devices for providing essentially zero d-c drift in said low paSs section.
Claim 8
Dependent Claim
196 words
Filtering apparatus in accordance with claim 6 capable of low pass, high pass, band pass and band reject operation comprising, an input terminal, means defining input, intermediate and output junctions, an output terminal, a low pass section, a high pass section, means for continuously coupling the output of said high pass section to said output terminal, means including said intermediate junction for grounding the input of said high pass section when said filtering means is in the low pass mode, means including said input junction for coupling said input terminal to the input of said high pass section when in the high pass and band reject mode, means including said input junction for coupling said input terminal to said input of said low pass section when in said low pass, band pass and band reject mode, means including said output junction and said intermediate junction for coupling the output of said low pass section to the input of said high pass section when in said band pass mode, and means including said output junction for coupling the output of said low pass section to said output terminal when in the band reject and low pass mode.
Claim 9
Dependent Claim
57 words
Filtering apparatus in accordance with claim 1 wherein said circuit means comprises a low pass section having an amplification loop with at least an input transistor and an output transistor and means for feeding back a portion of the signal on the collection of said output transistor to both the collector and emitter of said input transistor.
Claim 10
Dependent Claim
48 words
Filtering apparatus in accordance with claim 3 wherein said low pass section comprises first and second cascaded amplification loops having corresponding similar transistor amplification stages but with transistors of opposite types so that said cascaded loops coact to provide essentially zero d-c drift and a distortion cancelling effect.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-19 | 1976-06-19 | 1976-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-19 | 1980-06-19 | 1980-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-19 | 1984-06-19 | 1984-12-19 | $7700.00 | Window Closed / Lapsed |