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IP.com Disclosure Number: IPCOM000008173D
Original Publication Date: 1997-Jun-01
Included in the Prior Art Database: 2002-May-23

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John Burgan Fernando Hidalgo


A Liquid Crystal Displays operate on a zero biased AC waveform. The waveform is always present regardless of whether the pixels on the display are on or off. The Rh4S voltage of the wave- form controls the pixels on the display. The displays have a specified RMS "on" voltage range and an RMS "off' voltage range. These ranges are much smaller and much more critical on larger displays than on smaller ones. For example, on a small one line numeric display, a fixed LCD voltage works with all displays over a fairly wide range of temper- atures, but a larger four line alphanumeric display has an adjustable drive voltage that is compen- sated for temperature variations. On these larger displays, the voltage must be adjusted to optimize the contrast and viewing angle of the display. If the voltage varies, the contrast of the display varies. In addition, the contrast of the display varies with temperature, and the voltage must be adjusted with temperature to compensate and maintain a constant contrast.