Display device
View Patent ↗A display device able to hold a drain potential of an output transistor functioning as a constant current source constant even in a sampling period of another circuit, able to suppress a change due to leakage of a gate potential of the output transistor, able to obtain a uniform current source free from variation in current value of an output stage, and able to display a high quality image without occurrence of uneven luminance toward a scanning end part, wherein for example a current sample and hold circuit finishing a sampling and holding operation during a period where the sampling and holding operation of its own stage is ended and another stage is performing a sampling and holding operation is configured so as to carry a constant current corresponding to a sampled current by a thin film transistor through a node by operating a leakage elimination circuit.
1. A display device to which a video signal is supplied as a signal current, comprising:
a plurality of pixel circuits arrayed in a matrix;
data lines laid for every column of the matrix array of said pixel circuits and supplied with a signal current in accordance with luminance information; and
a horizontal selector having a plurality of sample and hold circuits provided corresponding to said data lines and sampling and holding the input video signal current and for sequentially operating the sample and hold circuits, point sequentially sampling and holding video signals at all sample and hold circuits, and outputting current values sampled and held in said plurality of sample and hold circuits to corresponding data lines, wherein
each sample and hold circuit comprises:
a field effect transistor having a source connected to a predetermined potential,
a first switch connected between a drain and a gate of said field effect transistor,
a second switch connected between the drain of said field effect transistor and a supply line of said signal current,
a capacitor connected between the gate of said field effect transistor and a predetermined potential, and
a leakage elimination circuit for supplying a current corresponding to the sampled signal current to the drain of said field effect transistor during a period when the sample and hold operation is finished and another sample and hold circuit performs a sample and hold operation.
2. A display device as set forth in claim 1 , wherein said leakage elimination circuit comprises a diode connected transistor connected between a predetermined potential and the drain of said field effect transistor and a third switch connected in series.
3. A display device to which a video signal is supplied as a signal current, comprising:
a plurality of pixel circuits arrayed in a matrix;
data lines laid for every column of the matrix array of said pixel circuits and supplied with a signal current in accordance with luminance information; and
a horizontal selector having a plurality of sample and hold circuits provided corresponding to said data lines and sampling and holding the input video signal current and for sequentially operating the sample and hold circuits, point sequentially sampling and holding a video signal in all sample and hold circuits, and outputting current values sampled and held at said plurality of sample and hold circuits to corresponding data lines, wherein
each sample and hold circuit comprises
a first field effect transistor having a source connected to a predetermined potential,
a second field effect transistor having a source connected to a drain of said first field effect transistor,
a first switch connected between a drain and a gate of said second field effect transistor,
a second switch connected between the drain of said second field effect transistor and a supply line of said signal current,
a third switch connected between the drain and a gate of said first field effect transistor,
a first capacitor connected between the gate of said first field effect transistor and a predetermined potential,
a second capacitor connected between the gate of said second field effect transistor and a predetermined potential, and
a leakage elimination circuit for supplying a current corresponding to the sampled signal current to the drain of said second field effect transistor during a period when the sample and hold operation is finished and another sample and hold circuit is performing a sample and hold operation.
4. A display device as set forth in claim 3 , wherein said leakage elimination circuit comprises a diode connected transistor connected between a predetermined potential and the drain of said second field effect transistor and a fourth switch connected in series.