Active matrix light emitting diode display

The present invention relates to active matrix display devices, and more particularly to drive circuitry that is located within each pixel of an active matrix display. An active matrix pixel within an active matrix display includes a photodiode that is optically connected to a light emitting diode within the pixel in order to detect a portion of the luminous flux that is generated by the light emitting diode. The photodiode discharges excess charge within the pixel in response to the detected portion of luminous flux. Once the excess charge is discharged, the light emitting diode stops emitting light. In an embodiment, the gate of a drive transistor is controlled by the charge on a storage node. If the charge on the storage node sets a voltage that exceeds the threshold voltage of the drive transistor then the drive transistor conducts. The amount of charge on the storage node above that which is needed to set the threshold voltage is referred to as the excess charge.