Design for Non Linearity Improvement of Current Steering Digital to Analog Convertor for Biomedical Applications

Abstract

A Digital to Analog Converter find its applications in almost all the fields where the newlinedata is to be measured and to be monitored at various places /systems including newlinehuman body. For biomedical portable devices which are used to measure and newlinecontrol parameters like ECG/EEG and in case of artificial retina implantations, there newlineis a great demand of high-speed high-resolution Digital-to-Analog converters newline(DAC) designs which offers good linearity characteristics. In addition, it is expected newlinethat such design/devices dissipate minimum power. newlineIn this work mainly the focuses are given for designing current steering DAC with newlinegood linearity characteristics using different Switching devices with variety of newlinecurrent sources for Improving Integral and differential Non linearity characteristics. newlineFor getting the advantages of binary weighted DAC and unary weighted current newlineDAC, the concept of segmented DAC has been adopted with various kinds of newlinecombinations. To optimize the performance in terms of linearity and power the newlineCurrent Steering DACs are designed using different types of switches like NMOS, newlineTransmission Gates and differential switches and combining the use of binary and newlineunary weighted DACs. For all the proposed designs, the simulations are carried out newlinein CMOS 180nm process results using standard design tools were obtained and newlinecompared with state of art results. newlineBased on the results of the designed DACs, it can be said that segmented approach newlinein current steering DAC with appropriate combination of no. of binary sources and newlineno. of Unary current sources at USB side and/or LSB side play an important role in newlinenon-linearity. Differential switch offers due advantages comparted to NMOS newlineswitches and Transmission Gate switch as a switching element. newlineThe most appropriate Design of current steering DAC for biomedical application is newlinesegmented Current DAC designed DAC with differential switches. DNL and INL newlineare 0.12 and 0.152 LSB with power consumption of 3.8uW, DNL is reduced by the newlinefactor of 7.58, INL is reduced by the fac