This　paper　presents　a　low-power　reference　voltage　buffer　with　fast　load　transient　response　that　can　be　used　to　drive　capacitive　loads.　The　circuit　is　based　on　an　improved　replica-biasing　source　follower　structure　that　combines　the　high　precision　of　the　closed　loop　and　the　high　bandwidth　of　the　open　loop,　and　it　meets　the　requirements　of　high　precision,　fast　load　transient　response　for　a　sigma-delta　modulator.　The　proposed　circuit　is　implemented　in　0.18　mu　m　CMOS　technology　provided　by　Semiconductor　Manufacturing　International　Corp.　(SMIC).　The　reference　voltage　buffer　is　combined　with　a　sigma-delta　modulator.　The　result　shows　that　when　the　load　capacitor　is　10pF,　the　settle　time　is　134ns,　the　quiescent　current　is　81.5　mu　A,　and　the　chip　area　is　117　mu　m　x　220　mu　m.