US4855627A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Filter circuit
Assignee: Toshiba Corp
•
Filing: 1988-01-13
•
Granted: 1989-08-08
•
Expires: 2008-01-13
Abstract
Abstract A filter circuit for filtering an input signal including a DC component signal with a prescribed DC level and an AC component signal. The filter circuit includes a time constant circuit for imparting the input signal with prescribed frequency characteristics, the time constant circuit including a variable impedance device and a capacitor, and a control signal source for supplying a control signal for adjusting the impedance of the variable impedance device, the control signal source including a DC source for generating a DC control signal and a compensation source for generating a compensation signal equivalent to the AC component signal of the input signal.
Inventors
- 👤 Hisakazu Hitomi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:12
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1291
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
100 words
A filter circuit for filtering an input signal including a DC component signal with a prescribed DC level and an AC component signal comprising: time constant circuit means for imparting the input signal with prescribed frequency characteristics, the time constant circuit means including a variable impedance device and a capacitor; and means for supplying a control signal for adjusting the impedance of the variable impedance device, the control signal supply means including DC source means for generating a DC control signal and compensation source means for generating a compensation signal equivalen to tthe AC component signal of the input signal.
Claim 2
Dependent Claim
100 words
A filter circuit for filtering an input signal including a DC component signal with a prescribed DC level and an AC component signal comprising: time constant circuit means for imparting the input signal with prescribed frequency characteristics, the time constant circuit means including a variable impedance device and a capacitor; and means for supplying a control signal for adjusting the impedance of the variable impedance device, the control signal supply means including DC source means for generating a DC control signal and compensation source means for generating a compensation signal equivalen to tthe AC component signal of the input signal.
Claim 3
Dependent Claim
23 words
The filter circuit of claim 1 including an integrated circuit device, the time constant circuit means being formed on the integrated circuit device.
Claim 4
Dependent Claim
17 words
The filter circuit of claim 2 wherein the variable impedance device includes at least one MOS FET.
Claim 5
Dependent Claim
37 words
The filter circuit of claim 3 wherein the time constant circuit means include first and second time constant circuits connected in series, said first and second time constant circuits each including a MOS FET and a capacitor.
Claim 6
Dependent Claim
24 words
The filter circuit of claim 4 wherein the control signal supply means is connected to the gate terminals of each of the MOS FETs.
Claim 7
Dependent Claim
46 words
The filter circuit of claim 5 further comprising a third time constant circuit and wherein the gate terminals of each MOS FET except the MOS FET of said first time constant circuit is connected to the control signal supply means through said third time constant circuit.
Claim 8
Dependent Claim
47 words
The filter circuit of claim 6 further comprising source means for generating a second compensation signal equivalent to the AC component signal of the input signal, and wherein the second compensation signal source means is connected to the back gate terminals of each of the MOS FETs.
Claim 9
Dependent Claim
18 words
The filter circuit of claim 7 wherein the second compensation signal source means includes an emitter follower circuit.
Claim 10
Dependent Claim
38 words
The filter circuit of claim 8 wherein the back gate terminals of each MOS FET except the MOS FET of said first time constant circuit is connected to the emitter follower circuit through a fourth time constant circuit.
Claim 11
Dependent Claim
32 words
The filter circuit of claim 9 further comprising a buffer amplifier connected between each of said first, second, third, and fourth time constant circuits and an output terminal of said filter circuit.
References Cited (Backward Citations)
US3805178A
Cited
US4040081A
Cited
US4063184A
Cited
US4288707A
Cited
GB2019151A
Cited
US4277749A
Cited
US4468749A
Cited
US4393351A
Cited
US4651034A
Cited
US4575650A
Cited
US4623854A
Cited
US4543534A
Cited
US4721870A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-08-07 | 1993-02-06 | 1993-08-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-07 | 1997-02-06 | 1997-08-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-07 | 2001-02-06 | 2001-08-08 | $7700.00 | Window Closed / Lapsed |