| 摘要 |
PROBLEM TO BE SOLVED: To prevent off current from flowing through a switching element and to keep stable operation by high setting an offset voltage added to signal potential applied to the signal input side of the switching element so as not to be affected with the fluctuation in the threshold value of the switching ele ment. SOLUTION: A video signal is generated by adding a video component to grounded potential VSS in an odd numbered horizontal scan period HO, and subtracting the video component from source potential VDD in an even number-th horizontal scan period HE. At this time, the offset of a fixed level is imparted at every polarity. That is, a reference level set in a top of each horizontal scan period is set so as to become higher than the grounded potential VSS in a positive polarity, and to become lower than the source potential VDD in a negative polarity. In such a case, the offset voltageΔV when the video signal is the positive polarity is set large so that the off current doesnot flow through a thin film transistor as the switching element even when operation characteristics are varied.
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