US6201442B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Amplifying circuit
Assignee: Individual
•
Filing: 1996-03-27
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Granted: 2001-03-13
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Expires: 2016-03-27
Abstract
Abstract An amplifier is provided for audio or instrumentation applications which exhibits radically improved performance over existing amplifiers of comparable cost. In a preferred embodiment, the amplifier comprises two operational amplifiers (A 1 , A 2 ) connected in cascade, where feedback elements (Cf 2 , Rf 2 ) are connected across the second op amp (A 2 ) to cause an intermediate voltage signal (Z) to be substantially advanced in phase. In this embodiment, a capacitor (Cf 1 ) is also connected across the first op amp (A 1 ), and an outer DC loop is provided with damping circuitry (Cf 3 ) to reduce the closed loop gain at high frequencies, stabilizing the combination. The composite amplifier has performance far exceeding a conventional stand-along op amp and is very cheap to construct.
Inventors
- 👤 Anthony Michael James
- 👤 William James Hildebrandt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:21
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/34; H03F3/343; H03F3/347; H03F1/00; H03F1/08; H03F1/083; H03F2200/00; H03F2200/261
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
135 words
An amplifying circuit high open loop gain for amplifying an input voltage signal to produce an output voltage signal, including an upstream first amplifying stage connected in cascade with a downstream second amplifying stage within an outer loop, said outer loop providing substantially linear amplification over an operating frequency range suitable for audio or instrumentation applications, wherein said second amplifying stage has connected thereto or associated therewith feedback means for providing that when said input voltage signal comprises a sinusoidal input voltage signal within an upper audible frequency range, an intermediate voltage signal measured at an intermediate point of the forward path of the amplifying circuit between the first and second amplifying stages is substantially phase advanced with respect to a notional non-advanced phase, the intermediate voltage signal remaining substantially phase advanced with current load.
Claim 2
Dependent Claim
135 words
An amplifying circuit high open loop gain for amplifying an input voltage signal to produce an output voltage signal, including an upstream first amplifying stage connected in cascade with a downstream second amplifying stage within an outer loop, said outer loop providing substantially linear amplification over an operating frequency range suitable for audio or instrumentation applications, wherein said second amplifying stage has connected thereto or associated therewith feedback means for providing that when said input voltage signal comprises a sinusoidal input voltage signal within an upper audible frequency range, an intermediate voltage signal measured at an intermediate point of the forward path of the amplifying circuit between the first and second amplifying stages is substantially phase advanced with respect to a notional non-advanced phase, the intermediate voltage signal remaining substantially phase advanced with current load.
Claim 3
Dependent Claim
29 words
An amplifying circuit as claimed in claim 1 wherein the high open loop gain of the amplifying circuit is greater than the open loop gain typical of operational amplifiers.
Claim 4
Dependent Claim
27 words
An amplifying circuit as claimed in claim 1 wherein the second amplifying stage and/or the first amplifying stage has an open loop gain typical of operational amplifiers.
Claim 5
Dependent Claim
39 words
An amplifying circuit as claimed in claim 1 wherein the second amplifying stage and/or the first amplifying stage has a transconductance typical of operational amplifiers, whereby the phase shift of the intermediate signal may remain unchanged under current load.
Claim 6
Dependent Claim
25 words
An amplifying circuit as claimed in claim 1 wherein the second amplifying stage and/or the first amplifying stage is a complete stand alone operational amplifier.
Claim 7
Dependent Claim
32 words
An amplifying circuit as claimed in claim 1 wherein the feedback means connected to the second operational amplifier is such that the phase advance of the intermediate signal is approximately 90 degrees.
Claim 8
Dependent Claim
23 words
An amplifying circuit as claimed in claim 1 wherein the phase advance of the intermediate signal is frequency independent over said frequency range.
Claim 9
Dependent Claim
39 words
An amplifying circuit as claimed in claim 1 constructed such that the DC open loop gain of the amplifying circuit is substantially the product of the open loop gains of each amplifying stage, substantially maintained across the power bandwidth.
Claim 10
Dependent Claim
52 words
An amplifying circuit as claimed in claim 1 wherein the feedback means is arranged to form with the second amplifying stage an integrator such that when a general input voltage signal is provided, the intermediate voltage signal is proportional to the differential of a voltage signal emerging from the second amplifying stage.
Claim 11
Dependent Claim
64 words
An amplifying circuit as claimed in claim 9 wherein the feedback means comprises a capacitor connected between the output of the second amplifying stage and an inverting input of the second amplifying stage, together with a resistor connected between an inverting input of the second amplifying stage and ground, and the intermediate signal is fed into the non-inverting input of the second operational amplifier.
Claim 12
Dependent Claim
78 words
An amplifying circuit as claimed in claim 9 wherein the feedback means comprises a capacitor connected between the output of the second amplifying stage and the inverting input of the second amplifying stage together with a resistor connected between said inverting input of the second amplifying stage and the intermediate point, the intermediate signal being fed into the inverting input of the second amplifying stage and the non-inverting input of the second amplifying stage being connected to ground.
Claim 13
Dependent Claim
19 words
An amplifying circuit as claimed in claim 1 wherein further feedback means is connected to the first amplifying stage.
Claim 14
Dependent Claim
34 words
An amplifying circuit as claimed in claim 12 wherein the further feedback means comprises a capacitor connected between an output of the first amplifying stage and the inverting input of the first amplifying stage.
Claim 15
Dependent Claim
40 words
An amplifying circuit as claimed in claim 1 wherein the outer loop comprises an outer loop damping means to reduce the closed loop gain of the amplifying circuit at high frequencies, thereby providing or enhancing stability of the amplifier circuit.
Claim 16
Dependent Claim
26 words
An amplifying circuit as claimed in claim 14 wherein the outer loop damping means comprises a capacitor in parallel with a resistor within said outer loop.
Claim 17
Dependent Claim
28 words
An amplifying circuit as claimed in claim 1 wherein the second amplifying stage is a power amplifying stage for providing large output currents and/or large output voltage swings.
Claim 18
Dependent Claim
114 words
A composite operational amplifier having improved stability and distortion, said composite amplifier comprising an upstream first operational amplifier connected in cascade with a downstream second operational amplifier, feedback means connected to the second operational amplifier such that the second operational amplifier acts as an integrator, and further feedback means connected to the first operational amplifier, and comprising a capacitor connected between the output and an input of the first operational amplifier, for providing that, in use, the composite operational amplifier may be placed within an outer loop of specified DC gain, and stabilising damping means connected to or associated with the outer loop in which the operational is placed to provide stable linear amplification.
Claim 19
Dependent Claim
114 words
A composite operational amplifier having improved stability and distortion, said composite amplifier comprising an upstream first operational amplifier connected in cascade with a downstream second operational amplifier, feedback means connected to the second operational amplifier such that the second operational amplifier acts as an integrator, and further feedback means connected to the first operational amplifier, and comprising a capacitor connected between the output and an input of the first operational amplifier, for providing that, in use, the composite operational amplifier may be placed within an outer loop of specified DC gain, and stabilising damping means connected to or associated with the outer loop in which the operational is placed to provide stable linear amplification.
Claim 20
Dependent Claim
124 words
A composite amplifier comprising: an upstream first operational amplifier connected in cascade with a downstream second operational amplifier; feedback means connected to or associated with the second operational amplifier; further feedback means connected to or associated with the first operational amplifier; an outer loop with resistive feedback to define a substantially linear amplification suitable for audio or instrumentation applications; and outer loop damping means connected to or associated with the outer loop to reduce the gain of the composite amplifier at high frequencies; said feedback means and further feedback means providing the composite amplifier with open loop gain substantially greater than the open loop gain of either operational amplifier and said outer loop damping means being adjusted so as to stabilise the composite amplifier.
Claim 21
Dependent Claim
124 words
A composite amplifier comprising: an upstream first operational amplifier connected in cascade with a downstream second operational amplifier; feedback means connected to or associated with the second operational amplifier; further feedback means connected to or associated with the first operational amplifier; an outer loop with resistive feedback to define a substantially linear amplification suitable for audio or instrumentation applications; and outer loop damping means connected to or associated with the outer loop to reduce the gain of the composite amplifier at high frequencies; said feedback means and further feedback means providing the composite amplifier with open loop gain substantially greater than the open loop gain of either operational amplifier and said outer loop damping means being adjusted so as to stabilise the composite amplifier.
Claim 22
Dependent Claim
26 words
An amplifier as claimed in claim 18 wherein said outer loop damping means comprises a capacitor connected in parallel with a resistor in said outer loop.
Claim 23
Dependent Claim
33 words
An amplifier as claimed in claim 18 wherein said first and second operational amplifiers are arranged such that the forward path of the amplifier passes through the non-inverting inputs of both operational amplifiers.
Claim 24
Dependent Claim
56 words
An amplifier as claimed in claim 20 wherein said feedback means comprises a capacitor between the output of the second operational amplifier and the inverting input thereof together with a resistor connected between said inverting input and ground, the non-inverting input of the second operational amplifier being connected to the output of the first operational amplifier.
Claim 25
Dependent Claim
75 words
An amplifier as claimed in claim 20 wherein said further feedback means comprises a discursion clamped capacitor connected between the output of the first operational amplifier and a point of the outer loop adjacent the inverting input of the first operational amplifier, together with a resistor connected between the inverting input of the first operational amplifier and ground, an input signal for the amplifier being connected to the non-inverting input of the first operational amplifier.
Claim 26
Dependent Claim
33 words
An amplifier as claimed in claim 18 wherein said first and second operational amplifiers are arranged such that the forward path of the amplifier passes through the inverting inputs of both operational amplifiers.
Claim 27
Dependent Claim
16 words
An amplifier as claimed in claim 18 wherein said feedback means has substantially no DC component.
Claim 28
Dependent Claim
17 words
An amplifier as claimed in claim 18 wherein said further feedback means has substantially no DC component.
Claim 29
Dependent Claim
23 words
An amplifier as claimed in claim 18 wherein said feedback means is differentiating, causing the second operational amplifier to act as an integrator.
Claim 30
Dependent Claim
19 words
An amplifier as claimed in claim 18 wherein said feedback means constitutes differentiating feedback modified by positive DC feedback.
Claim 31
Dependent Claim
14 words
An amplifier as claimed in claim 18 wherein said feedback means is double differentiating.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-03-12 | 2004-09-11 | 2005-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-03-12 | 2008-09-11 | 2009-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-03-12 | 2012-09-11 | 2013-03-13 | $7700.00 | Window Closed / Lapsed |