GAMMA CORRECTING CIRCUIT

PURPOSE:To obtain a gamma correcting characteristic coincident with the transmissive characteristic of a liquid crystal display device by providing a specified correcting circuit to compress a video signal more than a first voltage set in advance and to limit a compressing operation to a video signa...

Ausführliche Beschreibung

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Bibliographische Detailangaben
Hauptverfasser: ISHIGURO KAZUYUKI, ONO JUNZO
Format: Patent
Sprache:eng
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Beschreibung
Zusammenfassung:PURPOSE:To obtain a gamma correcting characteristic coincident with the transmissive characteristic of a liquid crystal display device by providing a specified correcting circuit to compress a video signal more than a first voltage set in advance and to limit a compressing operation to a video signal more than a second prescribed voltage higher than the first voltage. CONSTITUTION:When a video signal level VOUT1 of an output end 2 is less than the second voltage, out of first and second transistors Q9 and Q8, only the first transistor Q9 is turned ON and a voltage lower than the voltage of a first bias voltage source V, namely, than the first voltage only for a prescribed voltage is impressed to the base of a third transistor Q7. When a voltage to be loaded to the emitter of the third transistor Q7 is more than the first voltage, the third transistor Q7 is turned ON and when it is turned ON, the compressing operation of the video signal is executed. Next, when the video signal level VOUT1 of the output end 2 exceeds the second voltage, the third transistor Q7 is turned OFF and the compressing operation is limited. Thus, a gamma correcting circuit for the video signal can be obtained corresponding to the characteristic of the liquid crystal display device.