Patent US4555674A successfully refreshed from Google Patents.
US4555674A
Expired / Lapsed
US
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Power audio-amplifier with automatic adjustment of the bias current absorbed by the final stage
Assignee: STMicroelectronics SRL
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Filing: 1983-08-15
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Granted: 1985-11-26
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Expires: 2003-08-15
Abstract
Abstract A current control circuit coupled to the final stage of the amplifier automatically adjusts the bias current of the final stage so that it is low in the no-load state and higher in the load state. The low no-load value avoids useless energy leakages and heat dissipations, while the higher load value avoids "cross-over" distortions.
Inventors
- 👤 Sergio Palara
- 👤 Aldo Torazzina
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:46
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/30; H03F1/307; H03F3/00; H03F3/181; H03F3/183
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
79 words
A power audio amplifier, comprising: at least one amplifying stage; a final stage coupled to said at least one amplifying stage and having a bias current and an output adapted to provide an output current to a load having a load and a no-load state; and current control means, coupled to said final stage, for automatically changing said bias current between a low and a higher value when said load changes between said no-load and said load state, respectively.
Claim 2
Dependent Claim
79 words
A power audio amplifier, comprising: at least one amplifying stage; a final stage coupled to said at least one amplifying stage and having a bias current and an output adapted to provide an output current to a load having a load and a no-load state; and current control means, coupled to said final stage, for automatically changing said bias current between a low and a higher value when said load changes between said no-load and said load state, respectively.
Claim 3
Dependent Claim
67 words
An amplifier according to claim 1 wherein said final stage includes: first and second half stages coupled in parallel between said at least one amplifying stage and said final stage output, said first half stage providing a fraction of said output current to said current control means; and first and second bias chains coupled between said current control means and said first and second half stages, respectively.
Claim 4
Dependent Claim
70 words
An amplifier according to claim 2 wherein said current control means includes: detector means, for receiving said current fraction and providing a signal when said current fraction crosses a predetermined threshold; translator means, coupled to said detector means, for translating said signal into an actuating signal; and actuating means for causing said first and second bias chains to change said final stage bias current in response to said actuating signal.
Claim 5
Dependent Claim
40 words
An amplifier according to claim 3 further including at least one resistor connected in cascade with respect to said translator means, and wherein said detector means includes a capacitor having a discharge time fixed by said at least one resistor.
Claim 6
Dependent Claim
14 words
An amplifier according to claim 3 wherein said translator means includes a Darlington circuit.
Claim 7
Dependent Claim
28 words
An amplifier according to claim 3 wherein said actuator means includes a PNP transistor driven by said translator means, and an NPN transistor driven by said PNP transistor.
References Cited (Backward Citations)
US4331930A
Cited
US4439743A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-11-25 | 1989-05-27 | 1989-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-11-25 | 1993-05-27 | 1993-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-11-25 | 1997-05-27 | 1997-11-26 | $7700.00 | Window Closed / Lapsed |