The Key Technologies Of High-speed & High-precision Digital-analog Converter With All-NMOS Device

Digital to analog converter(DAC) is key device between digital system and analog system.It is also the important part of signal processing system.DAC is widely used in the area of communications,video and audio.The developing manufacture technologies of semiconductor and devices offers conditions for designing DAC by using of all-NMOS.Based on the study,comparison,analysis of some kinds of DAC system structure,working principle and operating mode,the paper put forward designing 10 bit 1GSample/S DAC by using form of segmented current-steering.The segmented current-steering is consisted of digital part and analog part.Based on the analysis of influence of current source array and switch array,current source and switch is designed by all-NMOS using process of TSMC 0.25μm.Through calculation,simulation and optimization,appropriate current source and switch is designed.The segment of"2+8"is adopted.Based on this segment,analog core circuit of all-NMOS 10-bit 1GSample/S DAC is designed.By simulating and optimizing the circuit using Cadence and Hspice,the result is period 1ns,output full range current 29.975mA,DNL<±0.5LSB,INL<±1LSB which is a perfect result.This analog core circuit is the basis of all-NMOS high-speed,high-precision DAC,and it is also an important step of research.