Digital-to-analog converter with gamma correction on glass substrate for TFT-panel applications

Low-temperature polysilicon (LTPS) technology has a tendency towards integrating all circuits on glass substrate. However, the poly-Si TFTs suffered poor uniformity with large variations in the device characteristics due to a narrow laser process window for producing large-grained poly-Si TFTs. The device variation is a serious problem for circuit realization on the LCD panel, so how to design reliable on-panel circuits is a challenge for system-on-panel (SOP) applications. In this work, a 6-bit R-string digital-to-analog converter (DAC) with gamma correction on glass substrate for TFT-panel applications is proposed. The proposed circuit, which is composed of a folded R-string circuit, a segmented digital decoder, and reordering of the decoding circuit, has been designed and fabricated in a 3-μm LTPS technology. The area of the new proposed DAC circuit is effectively reduced to about one-sixth compared to that of the conventional circuit for the same LTPS process.