US3786363A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Voltage-controlled low-pass filter
Assignee: United States Department of the Navy
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Filing: 1973-01-05
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Granted: 1974-01-15
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Expires: 1993-01-05
Abstract
Abstract An active low-pass filter whose cutoff frequency is a function of the input voltage to the filter comprising a series connection from the input to the filter to ground which consists of: (1) an input resistor r, (2) a capacitor C, and (3) a grounded resistor R. A series connection across the capacitor C comprises: (a) a feedback amplifier having two input leads, one of which is grounded, the other lead being connected to that side of the capacitor nearest ground; and (b) a feedback resistor Rho , one end being connected to the output of the feedback amplifier, the other end being connected to the ungrounded side of the capacitor. The feedback amplifier may be an operational amplifier. The output of the filter is at the junction of the resistors r and Rho and the capacitor C.
Inventors
- 👤 A Lelie
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 10:45
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1291
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
123 words
A low-pass filter whose cutoff frequency is a function of the input voltage to the filter comprising: a series connection from the input to the filter to ground comprising: 1. an input resistor r; 2. a capacitor C; 3. a grounded resistor R; a series connection across the capacitor C comprising: a feedback amplifier having two input leads, one of which is grounded, the other lead being connected to that side of the capacitor nearest ground; and a feedback resistor having one end being connected to the output of the feedback amplifier, the other end being connected to the ungrounded side of the capacitor; the output of the filter being at the junction of the resistors r and Rho and the capacitor C.
Claim 2
Dependent Claim
123 words
A low-pass filter whose cutoff frequency is a function of the input voltage to the filter comprising: a series connection from the input to the filter to ground comprising: 1. an input resistor r; 2. a capacitor C; 3. a grounded resistor R; a series connection across the capacitor C comprising: a feedback amplifier having two input leads, one of which is grounded, the other lead being connected to that side of the capacitor nearest ground; and a feedback resistor having one end being connected to the output of the feedback amplifier, the other end being connected to the ungrounded side of the capacitor; the output of the filter being at the junction of the resistors r and Rho and the capacitor C.
Claim 3
Dependent Claim
3 words
a capacitor C;
Claim 4
Dependent Claim
3 words
a capacitor C;
Claim 5
Dependent Claim
15 words
The low-pass filter according to claim 1, wherein the feedback amplifier is an operational amplifier.
Claim 6
Dependent Claim
47 words
The low-pass filter according to claim 2, wherein the input resistance r has a resistance in the range of 1,500 Omega ; the capacitance C is in the range of 1 Mu f; and the resistor R has a value in the range of 100 Omega .
Claim 7
Dependent Claim
84 words
a grounded resistor R; a series connection across the capacitor C comprising: a feedback amplifier having two input leads, one of which is grounded, the other lead being connected to that side of the capacitor nearest ground; and a feedback resistor having one end being connected to the output of the feedback amplifier, the other end being connected to the ungrounded side of the capacitor; the output of the filter being at the junction of the resistors r and Rho and the capacitor C.
Claim 8
Dependent Claim
84 words
a grounded resistor R; a series connection across the capacitor C comprising: a feedback amplifier having two input leads, one of which is grounded, the other lead being connected to that side of the capacitor nearest ground; and a feedback resistor having one end being connected to the output of the feedback amplifier, the other end being connected to the ungrounded side of the capacitor; the output of the filter being at the junction of the resistors r and Rho and the capacitor C.
Claim 9
Dependent Claim
75 words
The low-pass filter according to claim 2, further comprising: a third resistor, one lead of which is connecTed between the junction of the capacitor C and the grounded resistor R and the other lead of which is connected to the ungrounded input lead to the operational amplifier; and a fourth resistor, one end being connected to the ungrounded lead of the operational amplifier, the other end being connected to the output of the operational amplifier.
Claim 10
Dependent Claim
71 words
The low-pass filter according to claim 4, further comprising: a multiplier having three terminals, X, Y and Z; the X terminal being connected to an input direct-current voltage VDC; the Y terminal being connected to the output of the operational amplifier; the Z terminal being connected to the other end of the feedback resistor Rho ; the voltages at the terminals of the multiplier being related by the equation Z XY/10.
Claim 11
Dependent Claim
111 words
The low-pass filter according to claim 5 wherein the input resistor r has a value of resistance in the range of 1,600 Omega ; the capacitor C has a value of capacitance in the range of 1 Mu f; the resistor R has a value in the range of 100 Omega ; the feedback resistor Rho has a value in the range of 1,000 Omega ; the third resistor has a value of resistance in the range of 1, 000 Omega ; and the fourth resistor has a value of resistance in the range of 470 K Omega ; the gain A of the operational amplifier being equal to -47 VDC.
References Cited (Backward Citations)
US904030A
Cited
US3564441A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |