US3965441A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Parallel resonant circuit with feedback means for increasing Q
Assignee: Northrop Grumman Space and Mission Systems Corp
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Filing: 1975-06-20
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Granted: 1976-06-22
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Expires: 1995-06-20
Abstract
Abstract In a parallel resonant circuit having an inductor connected in parallel with a capacitor, a sensing resistor is connected in series with the inductor to sense the current in the resonant circuit. The voltage drop across the sensing resistor is applied to an operational amplifier and the amplified output voltage is fed back to the circuit loop out of phase with the sensed voltage drop so as to reduce the effective circuit resistance and thereby increase the circuit Q.
Inventors
- 👤 Neal L. Roy
- 👤 David O. Hansen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 02:28
CPC Classifications
H; H03; H03H; H03H5/00; H03H5/12; H04; H04B; H04B1/00; H04B1/06; H04B1/16; H04B1/163
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
129 words
A parallel resonant circuit, comprising: a. a capacitor and an inductor having a first side of each thereof connected in common; b. a resistor connected in series with the second side of said inductor to sense the current in said resonant circuit; and c. an operational amplifier having its non-inverting input terminal connected to the side of said resistor that is connected in common with said inductor, its inverting input terminal connected to the opposite side of said resistor, and the output terminal connected to the second side of said capacitor; said operational amplifier serving to introduce a negative resistance into said resonant circuit that is greater than that of said series resistor and thereby to effectively reduce the inherent resistance of said inductor and increase the Q thereof.
Claim 2
Dependent Claim
129 words
A parallel resonant circuit, comprising: a. a capacitor and an inductor having a first side of each thereof connected in common; b. a resistor connected in series with the second side of said inductor to sense the current in said resonant circuit; and c. an operational amplifier having its non-inverting input terminal connected to the side of said resistor that is connected in common with said inductor, its inverting input terminal connected to the opposite side of said resistor, and the output terminal connected to the second side of said capacitor; said operational amplifier serving to introduce a negative resistance into said resonant circuit that is greater than that of said series resistor and thereby to effectively reduce the inherent resistance of said inductor and increase the Q thereof.
Claim 3
Dependent Claim
24 words
The invention according to claim 1, and further including means within said operational amplifier for altering the gain thereof to alter the negative resistance.
Claim 4
Dependent Claim
54 words
The invention according to claim 1, and further including means within said operational amplifier for adjusting the gain thereof so that the negative resistance is greater in magnitude than the resistances represented by the sum of the resistances of said series resistor and said inductor, whereby said parallel resonant circuit constitutes an oscillatory circuit.
Claim 5
Dependent Claim
55 words
The invention according to claim 1, wherein said operational amplifier comprises first and second transistors of a differential transistor pair connected across said sensing resistor, and an amplifying transistor having its input circuit coupled to the output circuit of the first transistor of said differential pair and having its output circuit coupled to said capacitor.
Claim 6
Dependent Claim
29 words
The invention according to claim 4, wherein the output circuit of said amplifying transistor is also coupled to the input circuit of the second transistor of said differential pair.
References Cited (Backward Citations)
US3470500A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-06-22 | 1979-12-22 | 1980-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-06-22 | 1983-12-22 | 1984-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-06-22 | 1987-12-22 | 1988-06-22 | $7700.00 | Window Closed / Lapsed |