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Patent US5264804A successfully refreshed from Google Patents.
US5264804A
Expired / Lapsed
US
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Lowpass filter with improved D.C. offset performance
Assignee: Toshiba Corp
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Filing: 1992-02-05
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Granted: 1993-11-23
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Expires: 2012-02-05
Abstract
Abstract A lowpass filter with improved D.C. offset characteristics is disclosed. The lowpass filter includes an adjustable amplifier, an offset detecting circuit for producing an offset signal proportional to the D.C. offset between the voltage from the adjustable amplifier and the voltage to the lowpass filter, and a feedback circuit for producing a feedback signal in response to the offset signal which controls the adjustable amplifier to reduce the D.C. offset.
Inventors
- 👤 Timothy R. Fox
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:14
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/45; H03F3/45071; H03F3/45479; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1217
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
123 words
A lowpass filter having a filter input that receives an input signal having a D.C. component and a filter output that provides an output signal, comprising: means for lowpass filtering the input signal to produce a filtered signal; adjustable amplifying means for amplifying the filtered signal to produce the output signal; offset detecting means connected to the filter input and the filter output for producing an offset signal corresponding to the D.C. offset between the output signal and the input signal; and feedback means connected to the offset detecting means and the adjustable amplifying means, for producing a feedback signal corresponding to the offset signal and for controlling the adjustable amplifying means to reduce any D.C. offset between the input and output signals.
Claim 2
Dependent Claim
123 words
A lowpass filter having a filter input that receives an input signal having a D.C. component and a filter output that provides an output signal, comprising: means for lowpass filtering the input signal to produce a filtered signal; adjustable amplifying means for amplifying the filtered signal to produce the output signal; offset detecting means connected to the filter input and the filter output for producing an offset signal corresponding to the D.C. offset between the output signal and the input signal; and feedback means connected to the offset detecting means and the adjustable amplifying means, for producing a feedback signal corresponding to the offset signal and for controlling the adjustable amplifying means to reduce any D.C. offset between the input and output signals.
Claim 3
Dependent Claim
17 words
The lowpass filter of claim 1, wherein the lowpass filtering means includes a switched capacitor lowpass filter.
Claim 4
Dependent Claim
33 words
The lowpass filter of claim 1, wherein the adjustable amplifying means includes an operational amplifier and an adjustable resistor connected to the operational amplifier for adjusting the gain of the adjustable amplifying means.
Claim 5
Dependent Claim
16 words
The lowpass filter of claim 1, wherein the offset detecting means includes a voltage divider circuit.
Claim 6
Dependent Claim
25 words
The lowpass filter of claim 1, wherein the feedback means includes an integrator means for integrating the offset signal produced by the offset detecting means.
Claim 7
Dependent Claim
22 words
The lowpass filter of claim 5, wherein the integrator means includes a resistor and a capacitor both connected to an operational amplifier.
Claim 8
Dependent Claim
20 words
The lowpass filter of claim 5, wherein the integrator means includes a means for adjusting offset of the integrator means.
Claim 9
Dependent Claim
26 words
The lowpass filter of claim 6, wherein the feedback means further includes voltage limiting means connected to the capacitor to limit voltage buildup across the capacitor.
Claim 10
Dependent Claim
16 words
The lowpass filter of claim 8, wherein the voltage limiting means includes a diode Tee circuit.
Claim 11
Dependent Claim
25 words
The lowpass filter of claim 1, wherein the feedback means produces a feedback signal which is opposite in polarity with respect to the offset signal.
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) | 1996-11-22 | 1997-05-24 | 1997-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-11-22 | 2001-05-24 | 2001-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-11-22 | 2005-05-24 | 2005-11-23 | $7700.00 | Window Closed / Lapsed |