Liquid crystal display apparatus

Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix

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345 98, 345211, G09G 336

Patent

active

054772346

ABSTRACT:
A drive circuit is disclosed for a liquid crystal display apparatus of the active matrix type having a large number of gray levels that can be displayed. The drive circuit comprises a plurality of sections each including a sample-and-hold circuit 22. The sample-and-hold circuit 22 has a plurality of switches Sw 1 through Sw 4. To these switches are separately supplied different ramp signals Vr 1 through Vr 4 from a ramp generator circuit 24 shared by all the sections. These ramp signals have waveforms which respectively assume a plurality of different voltage levels and are shifted from each other by a predetermined voltage level. The decoder 21 selects one of the switches Sw 1 through Sw 4 and a specific one of the voltage levels in the ramp signal applied to that selected switch depending on the gray scale data in the latch 20. The output of the sample-and-hold circuit is transmitted to the data line 7a via a buffer 23.

REFERENCES:
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patent: 4766430 (1988-08-01), Gillette et al.
patent: 4841294 (1989-06-01), Clerc
patent: 5170155 (1992-12-01), Plus et al.
patent: 5214417 (1993-05-01), Yamazaki
patent: 5266936 (1993-11-01), Saitoh
patent: 5337070 (1994-08-01), Kitajima et al.

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