This paper presents the first demonstration of amorphous silicon (a-Si:H) thin film transistor (TFT) circuit integration on plastic substrates. The circuits compensate for material shortcomings such as metastable threshold voltage (VT) shift and high contact resistance, to supply stable and predictable currents to drive organic light emitting diode (OLED) displays on plastic. Various drive circuits were fabricated and tested. The simplest pixel driver circuit possible is the two TFT voltage-programmed circuit, which is very susceptible to any shift in VT of the drive TFT. To overcome this problem, we have developed current-programmed pixel circuits based on the current mirror circuit family, which include the simple and cascode current mirrors. The OLED current in these circuits is virtually independent of any VT shift or mobility variation in the drive TFT. Results show that the circuits provide higher linearity and dynamic range than currently available pixel circuits while minimizing the pixel area.
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