A new Row Voltage Amplitude Modulation (RVAM) method has been proposed. The proposed method has been applied to the implementation of a video-rate 8-gray Super Twisted Nematic Liquid Crystal Display (STN-LCD). Multi-line selection (MLS) method is used to obtain a fast STN-LCD with less crosstalk. 6 lines are selected at a time and each line is selected 8 times per frame. Though a conventional RVAM method makes it possible to realize a multi-gray STN-LCD with simple circuit configuration, high voltage and low selection ratio are serious problems. For example, when a conventional RVAM is applied to an 8-gray LCD with 240 rows, 28 V power supply is needed and the maximum selection ratio is only 1.0548 which is much lower than that of the theoretical maximum 1.0668. A proposed RVAM method makes it possible to use a conventional digital driver IC with low power supply of 20.5 V and to achieve a selection ratio of 1.0647 when applied to an 8-gray LCD with 240 rows. The implemented LCD has shown good images but with vertically repeated crosstalk and vertical crosstalk. It has been proved that the vertically repeated crosstalk is due to the difference of row signal frequency. Some methods are proposed to reduce the crosstalk.
