Apparatus and method for driving signal electrodes for liquid crystal display devices

Claim 1

An image display device including a signal electrode drive apparatus, comprising: (a) A/D converter means for sampling a video signal m times in accordance with a sampling clock within a period of an effective horizontal display and converting said video signal to n-bit digital data, where m is an integer; (b) latch circuit means including m stages of shift registers and m buffer registers; (c) one shift register in each stage for successively shifting a latch pulse in synchronism with reference clocks, to generate m latch clocks with different phases, and each of said buffer register being adapted for latching in parallel fashion said digital n-bit video data in synchronism with said latch clocks output from said shift registers, the buffer registers of each stage being coupled to receive said digital n-bit video data; (d) intensity modulation pulse generating circuit means for generating n kinds of intensity modulation pulses; (e) m-stage logic circuit means arranged to receive said n kinds of intensity modulation pulses from said pulse generating circuit and said n-bit digital data from said buffer circuit, said logic circuit means producing gradation signals having 2 n kinds of pulse widths corresponding to said digital data; (f) voltage selecting circuit means for decoding said gradation signals from said logic circuit means and for producing an output signal that varies with said gradation signals; and (g) dot matrix liquid crystal display panel means of the twist nematic type and including a signal electrode arranged to be driven in response to an output signal from said voltage selecting circuit.