Patent US3879674A successfully refreshed from Google Patents.
US3879674A
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US
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Automatic gain control circuit
Assignee: Unisys Corp
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Filing: 1973-12-27
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Granted: 1975-04-22
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Expires: 1993-12-27
Abstract
Abstract An automatic gain control circuit for setting the gain of a read amplifier in response to a preamble signal level by adjusting the bias on the amplifier. The amplifier''s gain is initially set at its maximum, and if the peak level of an analog form of the amplifier output overcomes a compared reference, the comparing circuitry emits a pulse which triggers capacitor-driving circuitry to charge a capacitor. The resultant variation in the capacitor''s voltage adjusts the amplifier bias via an emitterfollower to reduce the amplifier gain and output analog signal levels. Once the analog level drops below the reference, the capacitor voltage is no longer affected, and after the preamble, the charging circuitry is positively disabled. Finally, the capacitor is discharged to prepare for a subsequent read operation.
Inventors
- 👤 Thomas J Dragon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:10
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3005; G; G06; G06K; G06K7/00; G06K7/08; G11; G11B; G11B5/00; G11B5/02; G11B5/027; G11B5/035
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
185 words
An automatic gain control system employed in a data reading system for adjusting the amplitude level of a preamble signal train to a desired level represented by a settable reference level prior to a read operation comprising: a read amplifier supplied with said preamble signal train, having its bias set initially for amplifying said preamble signal train above said desired level and having a first bias terminal; means for generating an analog form of the amplified preamble signal, said form having peaks representative of the level of said amplified preamble signal; comparator means for comparing said analog form to said settable reference level and for generating a trigger pulse when said analog form exceeds said reference level; driver circuitry for transferring an increment of charge in response to each said trigger pulse; means for accumulating each said increment of transferred charge, thereby developing a voltage; buffer means for isolatinG said voltage and applying said voltage to said first bias terminal of said amplifier, thereby incrementally lowering the gain of said amplifier; and means for removing said accumulated stored charge after completion of said read operation.
Claim 2
Dependent Claim
185 words
An automatic gain control system employed in a data reading system for adjusting the amplitude level of a preamble signal train to a desired level represented by a settable reference level prior to a read operation comprising: a read amplifier supplied with said preamble signal train, having its bias set initially for amplifying said preamble signal train above said desired level and having a first bias terminal; means for generating an analog form of the amplified preamble signal, said form having peaks representative of the level of said amplified preamble signal; comparator means for comparing said analog form to said settable reference level and for generating a trigger pulse when said analog form exceeds said reference level; driver circuitry for transferring an increment of charge in response to each said trigger pulse; means for accumulating each said increment of transferred charge, thereby developing a voltage; buffer means for isolatinG said voltage and applying said voltage to said first bias terminal of said amplifier, thereby incrementally lowering the gain of said amplifier; and means for removing said accumulated stored charge after completion of said read operation.
Claim 3
Dependent Claim
30 words
The automatic gain control system of claim 1 wherein said amplifier is a standard amplifier and said first bias terminal is a standard terminal for receiving a constant reference voltage.
Claim 4
Dependent Claim
23 words
The automatic gain control system of claim 1 wherein said accumulating means is a capacitor and said buffer means is an emitter follower.
Claim 5
Dependent Claim
50 words
The automatic gain control system of claim 1 wherein said data reading system includes means for producing a synchronizing pulse and said automatic gain control system further includes means for coupling said synchronizing pulse to said comparator means, thereby precluding the emission of said trigger pulses by said comparator means.
Claim 6
Dependent Claim
66 words
The automatic gain control system of claim 1 wherein said analog form comprises a train of analog pulses and further including: means responsive to each said analog pulse for producing a rectangular pulse which begins and ends in synchronization with each said analog pulse; and gate means responsive only upon coincidence of a said rectangular pulse and a said trigger pulse for activating said driver circuit.
Claim 7
Independent Claim
105 words
A method of automatic gain control for setting the gain of a read amplifier to produce a desired output level in response to each of a series of preamble signal trains having variable levels comprising the steps of: initially fixing the gain of said amplifier such that the initial level of each said preamble signal train at the output of said amplifier is always greater than said desired output level; developing an analog pulse train representative of the output level of said preamble signal train; and decrementing the gain of said amplifier in response to each excess of an analog pulse over said desired level.
Claim 8
Independent Claim
105 words
A method of automatic gain control for setting the gain of a read amplifier to produce a desired output level in response to each of a series of preamble signal trains having variable levels comprising the steps of: initially fixing the gain of said amplifier such that the initial level of each said preamble signal train at the output of said amplifier is always greater than said desired output level; developing an analog pulse train representative of the output level of said preamble signal train; and decrementing the gain of said amplifier in response to each excess of an analog pulse over said desired level.
Claim 9
Independent Claim
105 words
A method of automatic gain control for setting the gain of a read amplifier to produce a desired output level in response to each of a series of preamble signal trains having variable levels comprising the steps of: initially fixing the gain of said amplifier such that the initial level of each said preamble signal train at the output of said amplifier is always greater than said desired output level; developing an analog pulse train representative of the output level of said preamble signal train; and decrementing the gain of said amplifier in response to each excess of an analog pulse over said desired level.
Claim 10
Independent Claim
105 words
A method of automatic gain control for setting the gain of a read amplifier to produce a desired output level in response to each of a series of preamble signal trains having variable levels comprising the steps of: initially fixing the gain of said amplifier such that the initial level of each said preamble signal train at the output of said amplifier is always greater than said desired output level; developing an analog pulse train representative of the output level of said preamble signal train; and decrementing the gain of said amplifier in response to each excess of an analog pulse over said desired level.
Claim 11
Dependent Claim
81 words
The method of claim 6 wherein said step of decrementing the gain of said amplifier includes the steps of: detecting an excess of a said analog pulse over a reference level representative of said desired level; producing a trigger pulse in response to said detecting; producing a charging pulse in response to said trigger pulse; accumulating the increment of charge supplied by said charging pulse, thereby developing a voltage; and applying said voltage to a bias terminal of said read amplifier.
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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) | 1978-04-21 | 1978-10-21 | 1979-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-21 | 1982-10-21 | 1983-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-21 | 1986-10-21 | 1987-04-22 | $7700.00 | Window Closed / Lapsed |