Nonlinear R-2R Transistor-Only DAC

Abstract

A nonlinear current-division technique is proposed with the design parameters on the aspect ratio of transistors only. The design approach uses the linear voltage-to-current relation for MOS transistors in the triode region. The nonlinear characteristics of the output current can be obtained by adding additional transistors on the conventional R-2R transistor-only ladder. This work can be employed for the applications of gamma-corrected digital-to-analog converters in the display driving systems. The simulation and measurement results of R-2R transistor ladders using an n-type amorphous-silicon thin-film-transistor process confirm the design strategy practicably.