Patent ID: 8427398

Claim:
A picture element structure in a current programming type of active matrix organic light emitting diode (OLED), comprising: first and second transistors for selecting a driving picture element based upon a scan signal applied from an exterior, said first and second transistors being adapted to receive a data current; a capacitor for storing electric charges applied from the first and second transistors; a third transistor adapted to be selected by the first and second transistors, for writing the data current thereto and receiving an external power source; a fourth transistor having a gate that is coupled to a gate of the third transistor, for receiving a voltage based upon the electric charges stored in the capacitor to supply a current to a corresponding picture element, wherein gate voltages of the third transistor and fourth transistor are always equal to each other; an organic light emitting diode (OLED) for emitting light by a current flowing through said fourth transistor; and a fifth transistor connected in series to the fourth transistor and formed of a conductivity type of transistors different from that of said first to fourth transistors having the same conductivity type of transistors, a gate of said fifth transistor being coupled with a scan line, wherein during a gate selection session for writing the data current to the third transistor, the scan signal is low, the first and second transistors are turned on, the third transistor operates in a saturation area and the fourth transistor is turned off, and wherein after the gate selection session, the scan signal is high, the first and second transistors are turned off, the third transistor operates in a linear area, the fourth transistor operates in a saturation area, and a current I OLED flows through the third transistor operating in the linear area and the fourth transistor operating in the saturation area so that the current IOLED is scaled down compared with the data current.