This　paper　presents　an　improved　1st-order　fully　passive　noise-shaping　(NS)　scheme　for　NS　SAR　ADCs.　In　order　to　move　the　zero　and　pole　of　the　noise　transfer　function　(NTF)　closer　to　the　unit　circle,　a　structure　combining　charge　pump　and　two-input　comparator　is　used　to　provide　two　gain　factors　of　2　and　3,　respectively,　forming　an　NTF　with　zero　and　pole　located　at　(0.875,　0)　and　(-0.75,　0),　respectively.　The　improved　NTF　can　provide　better　noise　suppression　effect　than　conventional　NTFs.　To　ensure　the　stability　of　the　ADC,　a　gain　calibration　technique　is　proposed　for　the　two-input　comparator　to　ensure　the　gain　ratio　between　the　2　input　branches,　which　can　prevent　the　pole　from　moving　outside　the　unit　circle　because　of　the　gain　mismatch　between　the　comparator＇s　2　input　branches.　In　addition,　the　proposed　structure　can　merge　the　integration　cycle　into　the　sampling　phase　to　enhance　the　conversion　speed.　Based　on　the　proposed　idea,　an　NS　SAR　ADC　with　a　10-bit　DAC　is　designed　in　65-nm　CMOS,　with　post-layout　simulation　results　showing　that　a　76-dB　SNDR　is　achieved　with　2.5-MHz　signal　bandwidth　and　40-MS/s　sampling　rate.