A scan driver circuit for depletion-mode oxide TFTs with stable output waveforms

A scan driver circuit that generates stable output waveforms with the depletion-mode oxide thin-film transistor (TFT) is reported. The output waveforms of the conventional scan driver deteriorate as the threshold voltage of the TFT becomes negative. For the proper operation of a scan driver circuit composed of oxide TFTs, the TFTs in the circuit should be turned off with negative gate-to-source bias. In addition, the output of each stage should not be affected by the adjacent stages. In this study, a new scan driver circuit that satisfies these two criteria was designed and fabricated. The new scan driver circuit works successfully and exhibits no ripple in the output waveforms even though the threshold voltage of the TFTs is as low as −3 V.