US5258658A
Expired / Lapsed
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Gamma correction circuit
Assignee: Sharp Corp
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Filing: 1992-04-30
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Granted: 1993-11-02
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Expires: 2012-04-30
Abstract
Abstract A gamma correction circuit including a differential amplifier for generating a current which decreases as an input voltage increases; a current control circuit for generating a current which is zero when the input voltage is below a first set value, increases as the input voltage increases when the input voltage is in a range from the first set value and a second set value, and becomes constant when the input value exceeds the second set value; and a circuit for generating a voltage proportional to a sum of the above-mentioned currents.
Inventors
- 👤 Hiroyuki Morikawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:19
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/32; H03F1/3223; H04; H04N; H04N5/00; H04N5/14; H04N5/20; H04N5/202; H04N5/74; H04N5/7416; H04N5/7441
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
92 words
A gamma correction circuit comprising: first means for generating a first current which decreases as an input voltage increases; second means for generating a second current which is zero when said input voltage is below a first set value, increases as said input voltage increases when said input voltage is in a range from said first set value to a second set value, and becomes constant when said input voltage exceeds said second set value; and third means for generating a voltage proportional to a sum of said first and second currents.
Claim 2
Dependent Claim
92 words
A gamma correction circuit comprising: first means for generating a first current which decreases as an input voltage increases; second means for generating a second current which is zero when said input voltage is below a first set value, increases as said input voltage increases when said input voltage is in a range from said first set value to a second set value, and becomes constant when said input voltage exceeds said second set value; and third means for generating a voltage proportional to a sum of said first and second currents.
Claim 3
Dependent Claim
42 words
A gamma correction circuit according to claim 1, wherein said first means comprises a differential amplifier having a first transistor which receives said input voltage at a base thereof and a second transistor which receives a constant voltage at a base thereof.
Claim 4
Dependent Claim
43 words
A gamma correction circuit according to claim 2, wherein said second means comprises a current mirror circuit including two transistors whose bases are connected to each other, said second current flowing to collectors of said two transistors included in said current mirror circuit.
Claim 5
Dependent Claim
66 words
A gamma correction circuit according to claim 3, wherein said third means comprises a transistor having a base which is applied with a constant voltage, a collector which is connected to a power-supply line through a resistor, and an emitter which is connected to a collector of said second transistor and to a collector of one of said two transistors included in said current mirror circuit.
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) | 1996-11-01 | 1997-05-03 | 1997-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-11-01 | 2001-05-03 | 2001-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-11-01 | 2005-05-03 | 2005-11-02 | $7700.00 | Window Closed / Lapsed |