Pixel circuit, driving method, display device, and inspection method
A circuit is provided to drive a controlled current from a drive transistor into one electroluminescent element of a pixel array. The circuit is operable to compensate for threshold voltage variation of the drive transistor, thereby providing improved image quality. The circuit is suitable for implementation with p-channel MOSFETs and a conventional geometry having in order: substrate, TFT layer(s), anode, electroluminescent layer(s), cathode. A driving method for this circuit is provided. A display incorporating this circuit is provided. The circuit is operable to provide an inspection function prior to fabrication of the electroluminescent layer(s). An inspection method is provided.
1. A pixel circuit comprising:
a sampling transistor having a gate electrode controlled by a first scanning line and a second electrode connected to a signal line;
a driving transistor having a gate electrode connected to a third electrode of the sampling transistor, and having a source electrode and a drain electrode;
a light emitting element connected between a drain electrode of the driving transistor and a first power supply line and driven by current supplied from the driving transistor;
a storage capacitor connected between the gate and source electrodes of the driving transistor;
a switching transistor having a gate electrode controlled by a second scanning line, a second electrode connected to the source electrode of the driving transistor, and a third electrode connected to a preset potential line;
a diode-connected transistor having gate and second electrodes connected to the source electrode of the driving transistor and a third electrode connected to a second power supply line; and
a shunt transistor having a gate electrode controlled by a third scanning line, a second electrode connected to the drain of the driving transistor, and a third electrode connected to a sink potential line;
wherein one of the preset potential line and the sink potential line is connected to a test point that is operable to connect to a probe for measuring current through the driving transistor prior to formation of the light emitting element.
2. A display device having a plurality of pixels arranged in a matrix, comprising:
a plurality of signal lines;
a signal line driving circuit for driving the plurality of signal lines;
a plurality of first scanning lines;
a first scanning line driving circuit for driving the plurality of first scanning lines;
a plurality of second scanning lines;
a second scanning line driving circuit for driving the plurality of second scanning lines;
a plurality of third scanning lines;
a third scanning line driving circuit for driving the plurality of third scanning lines;
at least one preset potential line for supplying a preset potential;
at least one sink potential line for supplying a sink potential; and
each of the plurality of pixels further comprising:
a sampling transistor having a gate electrode controlled by one of the plurality of first scanning lines and a second electrode connected to one of the plurality of signal lines;
a driving transistor having a gate electrode connected to a third electrode of the sampling transistor, and having a source electrode and a drain electrode;
a light emitting element connected between a drain electrode of the driving transistor and a first power supply line and driven by current supplied from the driving transistor;
a storage capacitor connected between the gate and source electrodes of the driving transistor;
a switching transistor having a gate electrode controlled by one of the plurality of second scanning lines, a second electrode connected to the source electrode of the driving transistor, and a third electrode connected to one of the at least one preset potential line;
a diode-connected transistor having gate and second electrodes connected to the source electrode of the driving transistor and a third electrode connected to a second power supply line; and
a shunt transistor having a gate electrode controlled by one of the plurality of third scanning lines, a second electrode connected to the drain of the driving transistor, and a third electrode connected to one of the at least one sink potential line;
wherein one of the at least one preset potential line and the at least one sink potential line is connected to a test point that is operable to connect to a probe for measuring current through the driving transistor prior to formation of the light emitting element.