Patent ID: 7812798

Claim:
An organic light emitting diode (OLED) display device with high output impedance, comprising: a current source, comprising: a first MOS transistor comprising: a gate; a first node; and a second node; a second MOS transistor providing high impedance comprising: a gate; a first node, coupled to the second node of the first MOS transistor; and a second node; a first controller coupled to the gate of the first MOS transistor, providing a controlling signal for controlling a current through the first MOS transistor; a first voltage source coupled to the gate of the second MOS transistor, providing a first voltage to the gate of the second MOS transistor; and a second voltage source directly coupled to the first node of the first MOS transistor, providing a second voltage to the first MOS transistor; and an OLED equivalent module directly coupled to the second node of the second MOS transistor, generating a light according to a current through the second MOS transistor.