US4748633A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semiconductor laser drive circuit in laser beam printer
Assignee: Pentax Corp
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Filing: 1987-05-11
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Granted: 1988-05-31
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Expires: 2007-05-11
Abstract
Abstract A semiconductor laser drive circuit in which a constant current circuit responds to the voltage developed by the constant current across a grounded resistor and in which a buffer circuit, such as a base-grounded transistor, is interposed between the source of the constant current and the laser.
Inventors
- 👤 Kiyoshi Negishi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:28
CPC Classifications
H; H01; H01S; H01S3/00; H01S5/00; H01S5/04; H01S5/042; H01S5/06; H01S5/068; H01S5/06808
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
69 words
A semiconductor laser drive circuit, comprising: a semiconductor laser modulated in response to a modulated drive current; a first constant current circuit means for providing a constant drive current along a constant current path; means for modulating said constant drive current to obtain said modulated drive current; and buffer circuit means provided in said constant current path for isolating said current source from said voltage variations at said laser.
Claim 2
Dependent Claim
69 words
A semiconductor laser drive circuit, comprising: a semiconductor laser modulated in response to a modulated drive current; a first constant current circuit means for providing a constant drive current along a constant current path; means for modulating said constant drive current to obtain said modulated drive current; and buffer circuit means provided in said constant current path for isolating said current source from said voltage variations at said laser.
Claim 3
Dependent Claim
37 words
A laser drive circuit as recited in claim 1, wherein said buffer circuit comprises a transistor having a base held at a preset voltage and having a collector and an emitter through which said drive current passes.
Claim 4
Dependent Claim
37 words
A laser drive circuit as recited in claim 1, wherein said first constant current circuit means outputs a first constant current in response to a reference voltage developed by said first constant current across a grounded resistor.
Claim 5
Dependent Claim
19 words
A laser drive circuit as recited in claim 3, wherein said constant drive current is said first constant current.
Claim 6
Dependent Claim
29 words
A laser drive circuit as recited in claim 3, wherein said first constant current controls a second constant current circuit which is said source of said constant drive current.
Claim 7
Dependent Claim
61 words
A laser drive circuit as recited in claim 3, wherein said first constant current circuit comprises: an operational amplifier receiving on differential inputs a standard voltage and said reference voltage developed across said grounded resistor; and an amplifying transistor receiving on a control electrode an output of said operational amplifier and having a principal current electrode connected to said grounded resistor.
Claim 8
Dependent Claim
102 words
A semiconductor laser circuit as recited in claim 1, wherein said first constant current circuit means comprises: a first transistor providing said constant drive current on its principal current electrodes; a diode-connected second transistor, a base of which is connected to a base of said first transistor; and a negative feedback resistor connected to a principal current electrode of said second transistor for changing a base-emitter voltage of said first transistor in response to a change of a power supply of said second transistor; whereby said first transistor functions as a constant current source and receives biasing current from said second transistor.
Claim 9
Dependent Claim
71 words
A semiconductor laser drive circuit, comprising: a semiconductor laser modulated in response to a modulated drive current; a resistor grounded on one side; a constant current circuit for providing a constant drive current for said semiconductor laser in response to a reference voltage developed across said grounded resistor by a constant current of said constant current circuit; and means for modulating said constant drive current to obtain said modulated drive current.
Claim 10
Dependent Claim
71 words
A semiconductor laser drive circuit, comprising: a semiconductor laser modulated in response to a modulated drive current; a resistor grounded on one side; a constant current circuit for providing a constant drive current for said semiconductor laser in response to a reference voltage developed across said grounded resistor by a constant current of said constant current circuit; and means for modulating said constant drive current to obtain said modulated drive current.
Claim 11
Dependent Claim
57 words
A laser drive circuit as recited in claim 8, wherein said constant current circuit comprises: an operational amplifier receiving as differential input voltages a standard voltage and said reference voltage; and an amplifying transistor having a control electrode connected to an output of said operational amplifier and having a principal current electrode connected to said grounded resistor.
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) | 1991-05-31 | 1991-11-30 | 1992-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-31 | 1995-11-30 | 1996-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-31 | 1999-11-30 | 2000-05-31 | $7700.00 | Window Closed / Lapsed |