Patent US3598912A successfully refreshed from Google Patents.
US3598912A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Video amplifier with black level control
Assignee: US Philips Corp
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Filing: 1970-02-11
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Granted: 1971-08-10
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Expires: 1990-02-11
Abstract
Abstract A video amplifier circuit including a black level control circuit wherein a level-shifting circuit and a limiter circuit are incorporated in the control circuit between an output and an input of a video amplifier so as to eliminate the parts of the output signal of the video amplifier which are unimportant for the black level control.
Inventors
- 👤 Antonius Hendrikus Hu Nillesen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:52
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/16; H04N5/18; H04N5/185; H04N5/44; H04N5/57
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
206 words
A video amplifier circuit for a television picture display device comprising at least one video amplifier which includes an automatic level control circuit employing a time-selective level detection device having at least a first input which is connected to an output of the video amplifier, a second input which is coupled to an output of a pulse generator and a level detector having an output which is connected to a level control input of the video amplifier, characterized in that the level detection device comprises a combination circuit and a limiter circuit, a video signal input of said combination circuit being connected to the said first input and a further input being coupled to an output of the pulse generator while an output of the combination circuit is connected to an input of the limiter circuit and an output of the limiter circuit is connected to the level control input of the video amplifier, the output of the combination circuit is the sum of the video and pulse signals supplied thereto whereby; at least part of the video signal on the same side of the black level as the maximum white level originating from the output of the combination circuit is limited in the limiter circuit.
Claim 2
Dependent Claim
206 words
A video amplifier circuit for a television picture display device comprising at least one video amplifier which includes an automatic level control circuit employing a time-selective level detection device having at least a first input which is connected to an output of the video amplifier, a second input which is coupled to an output of a pulse generator and a level detector having an output which is connected to a level control input of the video amplifier, characterized in that the level detection device comprises a combination circuit and a limiter circuit, a video signal input of said combination circuit being connected to the said first input and a further input being coupled to an output of the pulse generator while an output of the combination circuit is connected to an input of the limiter circuit and an output of the limiter circuit is connected to the level control input of the video amplifier, the output of the combination circuit is the sum of the video and pulse signals supplied thereto whereby; at least part of the video signal on the same side of the black level as the maximum white level originating from the output of the combination circuit is limited in the limiter circuit.
Claim 3
Dependent Claim
105 words
A video amplifier circuit as claimed in claim 1, characterized in that the further input of the combination circuit is connected to the said second input of the level detection device, a pulse signal originating from the output of the pulse generator being combined in the combination circuit with the video signal fed to the video signal input at such an amplitude and polarity that the level to be detected in the level detection device in the combined signal at the output of the combination circuit occurs on the other side of the maximum white level in the video signal than the black level does.
Claim 4
Dependent Claim
54 words
A video amplifier circuit as claimed in claim 2, characterized in that the combination circuit is an adder circuit which includes series-arranged resistors between a terminal of the said video signal input and a terminal of the said further input, the junction of said resistors being connected to the input of the limiter circuit.
Claim 5
Dependent Claim
85 words
A video amplifier circuit as claimed in claim 3, characterized in tHat the said junction of the series arrangement is connected at one end through a diode in the limiter circuit and at the other end through a base-emitter junction of a transistor incorporated in the level detection circuit, which base-emitter junction has a direction of conductivity which is opposite to the diode, while the collector of the said transistor is connected to the output connected to the level control input of the video amplifier.
Claim 6
Dependent Claim
67 words
A video amplifier as claimed in claim 1, characterized in that the further input of the combination circuit is connected through a rectifier circuit to an output of the pulse generator and that the second input of the time-selective level detection device is connected to an input of the limiter circuit which has a level of limitation which is dependent on a signal at the second input.
Claim 7
Dependent Claim
100 words
A video amplifier circuit as claimed in claim 5, characterized in that the input of the limiter circuit connected to the output of the combination circuit is connected to the output of the limiter circuit and is connected to ground through a series arrangement of a plurality of diodes, while the other end of the diode connected to the input and the output of the limiter circuit is also connected to the collector of a transistor the base of which is connected to the input of the limiter circuit which input is connected to the output of the pulse generator.
References Cited (Backward Citations)
US2851520A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-09 | 1975-02-08 | 1975-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-09 | 1979-02-08 | 1979-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-09 | 1983-02-08 | 1983-08-10 | $7700.00 | Window Closed / Lapsed |