Patent US4524739A successfully refreshed from Google Patents.
Patent EP0116398A2 successfully refreshed from Google Patents.
EP0116398A2
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EP
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Gamma compensating circuit
Assignee: Sony Corp
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Filing: 1984-01-06
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Granted: —
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Expires: 2004-01-06
Abstract
Abstract A circuit having a nonlinear response characteristic provides gamma compensation to a video luminance signal and matches any desired output response curve by selecting the number of diodes connected as series-connected circuits in the compensation circuit. The relationship among the various numbers of series-connected diodes is dependent upon having a current flowing into an output circuit which is the same as a current flowing out of a collector circuit of a differential amplifier, to which the input video luminance signal is applied, and through series-connected diode circuit. These currents are maintained equal by use of a current-mirror circuit, which provides an input current to an output transistor that has in its emitter circuit one of the series-connected diode circuits, and the compensated luminance signal flows in the collector circuit thereof. The differential amplifier is stabilized and balanced by a difference amplifier connected in feedback across the collector leads of the differential amplifier in conjunction with a pedestal clamping synchronization signal and a capacitor to provide a balancing signal at the base lead of the second transistor of the differential transistor amplifier.
Inventors
- 👤 Joichi Sato
- 👤 Ryuji Shiono
- 👤 Tsutomu Nimura
- 👤 Toshiaki Isogawa
- 👤 Mitsuru Sato
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 21:08
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/20; H04N5/202
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
324 words
A circuit having a nonlinear response characteristic for providing gamma compensation to an input video luminance signal and using series-connected diode circuit to provide gamma compensation, characterized by; a differential transistor amplifier (Q 11 , Q 12' ) formed of a pair of transistors and having the input signal connected to a base lead of a first transistor (Q 11 ) and having the collector lead thereof connected to a reference potential through first diode circuit (D 1 ), the collector leads of the differential transistor amplifier (Q 11 , Q 12 ) being interconnected through a second diode circuit (D2), a current source (Q 14 , Q 15 ) is connected to supply a constant current to the differential transistor amplifier and to the first diode circuit (D 1 ), a difference amplifier (12) has inputs connected respectively to the collector circuits of the differential transistor amplifier (Q 11 , Q 12 ) and provides an output difference signal fed to the base lead of the second transistor (Q12) in the differential transistor amplifier, a capacitor (C 11 ) is arranged to connect the output signal from the difference amplifier to the reference potential, a current-mirror circuit (13) is connected to the first diode circuit (D 1 ), a third diode circuit (D 3 ) is connected to a collector lead of the differential transistor amplifier and to an output current (I 5 ) of a current-mirror circuit (13), whereby the current-mirror circuit operates to cause a current (I 5 ) flowing through the diode circuit (D 3 ) to equal a current (I 2 ) flowing through the first diode circuit (D 1 ); and an output circuit Q 6 is connected to the third diode circuit and is connected to the reference potential through a fourth diode circuit (D 4 ) for producing an output signal (i 6 ) that is a nonlinearly compensated reproduction of the input video luminance signal.
Claim 2
Dependent Claim
324 words
A circuit having a nonlinear response characteristic for providing gamma compensation to an input video luminance signal and using series-connected diode circuit to provide gamma compensation, characterized by; a differential transistor amplifier (Q 11 , Q 12' ) formed of a pair of transistors and having the input signal connected to a base lead of a first transistor (Q 11 ) and having the collector lead thereof connected to a reference potential through first diode circuit (D 1 ), the collector leads of the differential transistor amplifier (Q 11 , Q 12 ) being interconnected through a second diode circuit (D2), a current source (Q 14 , Q 15 ) is connected to supply a constant current to the differential transistor amplifier and to the first diode circuit (D 1 ), a difference amplifier (12) has inputs connected respectively to the collector circuits of the differential transistor amplifier (Q 11 , Q 12 ) and provides an output difference signal fed to the base lead of the second transistor (Q12) in the differential transistor amplifier, a capacitor (C 11 ) is arranged to connect the output signal from the difference amplifier to the reference potential, a current-mirror circuit (13) is connected to the first diode circuit (D 1 ), a third diode circuit (D 3 ) is connected to a collector lead of the differential transistor amplifier and to an output current (I 5 ) of a current-mirror circuit (13), whereby the current-mirror circuit operates to cause a current (I 5 ) flowing through the diode circuit (D 3 ) to equal a current (I 2 ) flowing through the first diode circuit (D 1 ); and an output circuit Q 6 is connected to the third diode circuit and is connected to the reference potential through a fourth diode circuit (D 4 ) for producing an output signal (i 6 ) that is a nonlinearly compensated reproduction of the input video luminance signal.
Claim 3
Dependent Claim
46 words
A circuit having a nonlinear response characteristic according to claim 1, in which the difference amplifier (12) is connected to receive a clamping synchronization signal (T 12 ) for providing a clamping level output fed to the differential transistor amplifier (Q 12 ) in response thereto.
Claim 4
Dependent Claim
71 words
A circuit having a nonlinear response characteristic according to claim 1, in which the first diode circuit (D1) includes (N - K) series-connected diodes, the second diode circuit (D 2 ) includes (k) diodes, the third diode circuit (D 3 ) includes (J - 1) series-connected diodes and the fourth diode (D 4 ) circuit includes (N - J - 1) series-connected diodes where N, K, and J are positive integers.
Claim 5
Dependent Claim
38 words
A circuit having a nonlinear response characteristic according to claim 1, in which the current-mirror circuit (13) is connected across a last one ( Dla ) of the first series-connected (N - K) diodes and the reference potential.
Claim 6
Dependent Claim
71 words
A circuit having a nonlinear response characteristic according to claim 4, in which the current-mirror circuit (13) comprises at least one current-mirror transistor (Q 5 ) having a base lead connected to the last diode (D la ) of said first diode circuit (D 1 ) and a collector lead connected to the third diode circuit (D 3 ) and also to the input of the output circuits (Q 6 ).
Claim 7
Dependent Claim
66 words
A circuit having a nonlinear response characteristic according to claim 5, in which the output circuit comprises at least one output transistor (Q 6 ) having a base lead connected to the collector lead of the current mirror transistor (Q 5 ) and in which the fourth diode circuit (D 4 ) comprises (J - 1) diodes connected in series, where J is a positive integer.
Claim 8
Dependent Claim
108 words
A circuit having a nonlinear response characteristic according to claim 6, in which the current-mirror circuit (13) includes a second current-mirror transistor (O 15 ) having a base lead connected to the base lead of the first current-mirror transistor (Q 5 ) and a collector lead connected to a fifth diode circuit (D 31 ) connected to the differential amplifier output (Q 12 ), and the output circuit comprises. a second output transistor (Q 61 ) having a base lead connected to the collector lead of the second current-mirror transistor (Q 51 ) and an emitter lead connected to the reference potential through a sixth diode circuit (D41).
Claim 9
Dependent Claim
36 words
A circuit having a nonlinear response characteristic according to claim 7, in which the sixth diode circuit (D 41 ) includes (J - J 1 - 1) series-connected diodes, where J 1 is a positive integer.
References Cited (Backward Citations)
No citation records indexed.
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