Current-dependent light-emitting element drive circuit for use in active matrix display device

An active matrix display device comprising:

• a plurality of first lines extending in parallel with one another;
• a plurality of second lines extending perpendicular to said first lines to form a plurality of cross points arranged in a matrix form;
• and
• a plurality of current-dependent light-emitting element drive circuits, each disposed at each of said cross points and connected to one of said first lines and one of said second lines at each of said cross points to form one of pixels in the display device, each of said current-dependent light-emitting element drive circuit comprising:
• constant current supplying means to be connected to a power source for supplying a constant current;
• said current-dependent light-emitting element connected in series with said constant current supplying means;
• and
• switching means connected in parallel with said current-dependent light-emitting element for controlling current flowing through said current-dependent light-emitting element from said constant current supplying means, said switching means being coupled with said first line and said second line and being controlled between an ON and an OFF conditions by selection signals selectively applied to said first and said second lines, wherein said constant current supplying means comprises a terminal to be connected to said power source and an opposite terminal connected to one of common connected points between said switching means and light-emitting element.

An active matrix display device comprising:

• scanning lines and data lines arranged in a matrix form on a substrate to form cross points at which pixels are disposed, each of said scanning lines being for supplying a pixel selection signal, each of said data lines being for supplying a drive voltage signal for one of pixels as selected;
• and
• a plurality of drive circuits as said pixels arranged at said cross points, each of said drive circuits comprising:
• a current-dependent light-emitting element arranged at said cross point;
• a current-control transistor connected in parallel to said light-emitting element;
• a switching transistor connected to said current-control transistor, one of said scanning lines and one of said data lines, and responsive to said pixel selection signal from said scanning line, for applying said drive voltage signal from said data line to said current-control transistor to control a current which flows through said current-control transistor;
• and
• constant current source having a terminal to be connected to a power source and an opposite terminal connected to one of common connection points between said current-control transistor and said light-emitting element, said constant current source providing a constant current of a constant current value from said opposite terminal, said constant current flows through said light emitting element when said current-control transistor is turned off.