A gamma-type current-mode digital-to-analog converter for active-matrix organic light-emitting diode display drivers

Abstract

This paper describes the design of a gamma-type current-mode digital-to-analog converter (DAC) for active-matrix organic light-emitting diode display (AMOLED) drivers. The proposed nonlinear DAC is composed of division-based bypassing DAC units for gamma correction. This multiple stack of DAC units dramatically reduces the chip size of the display driver while realizing more natural gamma correction. Moreover, it does not require an additional memory, such as a digital look-up table block and a DAC with a higher resolution, which can achieve significant manufacturing cost savings. Consequently, the proposed multi-stacked gamma-type DAC provides high area efficiency, low cost, and more natural gamma correction. The prototype 8-bit DAC is implemented in a TowerJazz 3.3 V CMOS process. The simulated gamma values of the double- and triple-stacked DAC units are varied from 1 to 2 and from 1 to 3, respectively. In addition, the Monte-Carlo simulation demenstrates that the proposed design shows uniform gamma transfer curves regardless of the process variation.