Gamma compensating circuit

Details Gamma compensating circuit Gamma compensating circuit

1984-01-04

1986-05-13

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358169, 358 32, H04N 5202, H04N 557, H04N 969

Patent

active

045890218

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.

REFERENCES:
patent: 3935478 (1976-01-01), Okada et al.
patent: 4015079 (1977-03-01), Satou et al.
patent: 4218706 (1980-08-01), Brinegar et al.
patent: 4393406 (1983-07-01), Lehmann

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