US4015079A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gamma correction circuit
Assignee: Toshiba Corp
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Filing: 1976-04-08
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Granted: 1977-03-29
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Expires: 1996-04-08
Abstract
Abstract A gamma correction circuit is disclosed which includes an amplifier for amplifying a video input signal, a series connection of diode connected transistors whose input terminal is coupled to the output terminal of the amplifier and a cascade connection of emitter follower transistors whose output terminal is connected to the output terminal of the series connection of the diode connected transistors and is grounded through a resistor and whose input terminal is supplied with control signals.
Inventors
- 👤 Itsuzou Satou
- 👤 Kikuo Saitou
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 01:58
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/20; H04N5/202; H04N9/00; H04N9/64; H04N9/68; H04N9/69
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
280 words
A gamma correction circuit comprising: amplifying means for amplifying an input signal, said amplifying means including input and output terminals; a non-linear circuit having a first terminal and a second terminal and a plurality of series-connected diode means connected between said first terminal and said second terminal, the first terminal of said non-linear circuit being coupled to the output terminal of said amplifying means and each of said diode means being connected to have the same polarity so that current flows from the first terminal to the second terminal of said non-linear circuit, wherein the voltage of a signal appearing at the first terminal of said non-linear circuit is varied non-linearly in accordance with the change in the voltage of an input signal to said amplifying means; an emitter follower circuit having an input terminal and an output terminal and a plurality of cascaded emitter follower transistors connected between said input and output terminals of said emitter follower circuit, the output terminal of said emitter follower circuit being coupled to the second terminal of said non-linear circuit, each of said emitter follower transistors being connected so that current flows from the input terminal of the emitter follower circuit to the output terminal of the emitter follower circuit, said plurality of cascaded emitter follower transistors being equal in number to said plurality of diode means; and circuit means for applying a control signal coupled to the input terminal of said emitter follower circuit, for varying nonlinearity of said input signal; whereby a change due to ambient temperature in a voltage across said non-linear circuit is compensated by a change due to ambient temperature in a voltage across said emitter follower circuit.
Claim 2
Dependent Claim
280 words
A gamma correction circuit comprising: amplifying means for amplifying an input signal, said amplifying means including input and output terminals; a non-linear circuit having a first terminal and a second terminal and a plurality of series-connected diode means connected between said first terminal and said second terminal, the first terminal of said non-linear circuit being coupled to the output terminal of said amplifying means and each of said diode means being connected to have the same polarity so that current flows from the first terminal to the second terminal of said non-linear circuit, wherein the voltage of a signal appearing at the first terminal of said non-linear circuit is varied non-linearly in accordance with the change in the voltage of an input signal to said amplifying means; an emitter follower circuit having an input terminal and an output terminal and a plurality of cascaded emitter follower transistors connected between said input and output terminals of said emitter follower circuit, the output terminal of said emitter follower circuit being coupled to the second terminal of said non-linear circuit, each of said emitter follower transistors being connected so that current flows from the input terminal of the emitter follower circuit to the output terminal of the emitter follower circuit, said plurality of cascaded emitter follower transistors being equal in number to said plurality of diode means; and circuit means for applying a control signal coupled to the input terminal of said emitter follower circuit, for varying nonlinearity of said input signal; whereby a change due to ambient temperature in a voltage across said non-linear circuit is compensated by a change due to ambient temperature in a voltage across said emitter follower circuit.
Claim 3
Dependent Claim
28 words
A circuit as in claim 1, wherein: each of said diode means comprises a transistor having its base and collector electrodes coupled together for functioning as a diode.
Claim 4
Dependent Claim
13 words
A circuit as in claim 1, wherein: said circuit is an integrated circuit.
Claim 5
Dependent Claim
47 words
A circuit as in claim 1, wherein said amplifying means comprises: clamping circuit means for producing a direct current output signal, means for applying a video signal to said clamping circuit; and, differential amplifier means coupled to said clamping circuit for amplifying said direct current output signal.
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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) | 1980-03-28 | 1980-09-27 | 1981-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-28 | 1984-09-27 | 1985-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-28 | 1988-09-27 | 1989-03-29 | $7700.00 | Window Closed / Lapsed |