Patent ID: 7928932
Filing Date: 2011-04-19
Classification: G09G,H01L

Abstract:
1. A display element drive circuit comprising: an electric charge holding circuit which holds as a voltage component electric charges based on a gradation signal corresponding to display data; a write control circuit which supplies the gradation signal to the electric charge holding circuit at a timing of application of a selection signal; a current control type display element; and a driving current control circuit which generates a driving current based on the voltage component held in the electric charge holding circuit and supplies the generated driving current to the display element, wherein: the write control circuit comprises: (i) a write transistor formed by a field effect transistor including a current path and a control terminal, wherein one end side of the current path is connected to a signal line through which the gradation signal is supplied, the other end side of the current path is connected to the driving current control circuit, and the gradation signal flows through the current path at a timing of application of the selection signal so that a write current is supplied to the driving current control circuit, and (ii) a control transistor formed by a field effect transistor and including a current path and a control terminal, wherein a predetermined power supply voltage is applied to one end side of the current path, the other end side of the current path is connected to the driving current control circuit, and the selection signal is applied to the control terminal of the control transistor, wherein each of the write transistor and the control transistor has a specific construction, which includes a gate electrode that has a predetermined gate length and that constitutes the control terminal, and a drain electrode and a source electrode constituting said one end side of the current path and said other end side of the current path, wherein a source-side parasitic capacitance of the control transistor is set to a value smaller than a capacitance value of a drain-side parasitic capacitance of the control transistor, wherein with the specific construction of the write transistor: wherein said predetermined current value is a current value of a current which would flow through the current path between the drain and source electrodes, if a rectangular channel region formed between the source electrode and the drain electrode had gate widths respectively positioned on sides of the drain electrode and the source electrode set to said predetermined gate width, when the gate, source and drain electrodes are respectively set to the predetermined electric potentials, and wherein with the specific construction of the write transistor, one of the drain-side parasitic capacitance and the source-side parasitic capacitance which is formed in said one end side of the current path is set to a value smaller than a capacitance value of the other of the drain-side capacitance value and the source-side parasitic capacitance which is formed in said other end side of the current path.