| 摘要 |
An active matrix electroluminescent (EL) display device has a switching circuit for each display pixel which has a drive transistor ( 30 ) and a cascode transistor ( 32 ) in series with the associated EL display element ( 20 ). The switching circuit is operable in two modes, a first mode in which an input current is sampled by the drive transistor ( 30 ) and a second mode in which the drive transistor drives a current corresponding to the input current through the EL display element ( 20 ). This configuration uses the same transistor for current sampling as for current driving, thereby avoiding the need for matched transistors. The cascode transistor increases the output impedance and ensures that no voltage fluctuations pass to the drive transistor, so that a constant current supply is maintained.
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