Patent ID: 8089438

Claim:
A data line driver circuit for a display panel comprising: a digital-to-analog (D/A) converter circuit configured to convert two display data to be supplied into gradation voltages of first and second polarities, wherein said D/A converter circuit comprises: a first gradation voltage selecting circuit configured to control transistors of a first group to select one of gradation voltages of the first polarity based on a first display data of the two display data; a second gradation voltage selecting circuit configured to control transistors of a second group to select one of gradation voltages of the second polarity based on a second display data of the two display data; a first gradation voltage signal line configured to transfer the first polarity gradation voltage selected by said first gradation voltage selecting circuit; a second gradation voltage signal line configured to transfer the second polarity gradation voltage selected by said second gradation voltage selecting circuit; and a test switching circuit configured to operate in response to a test signal, wherein said test switching circuit forms a short-circuit between said first and second gradation voltage signal lines in response to the test signal, to allow a leakage current to be measured between a drain and a source in each of one or more of said transistors of said first group and one or more of said transistors of said second group.