Small-area DAC using adaptive body bias scheme for AMOLED data driver ICs

A small-area digital-to-analogue converter (DAC) using an adaptive body bias scheme is proposed for active-matrix organic light-emitting diode (AMOLED) data driver ICs. The proposed scheme adjusts the body bias applied to the P-type (PMOS) decoder according to the average picture level (APL) and maintains a low on-resistance of the PMOS decoder at a high APL. This enables reduction of the DAC area by realising the upper-half decoder using only PMOS switches, unlike conventional DACs which use both PMOS and N-type switches. A 20-channel data driver IC is fabricated using a 0.18 μm HVCMOS technology with 1.8 V/18 V devices. The proposed DAC occupies 33% less area than the conventional DAC and the measured differential nonlinearity and integral nonlinearity are +0.09/-0.1 and +0.36/-0.47 LSB, respectively.