This　paper　presents　a　4-channel　neural　stimulation　integrated　circuit　design　with　exponential　current　output.　Using　exponentially　decaying　current　output　for　neural　stimulation,　the　excessive　headroom　voltage　of　the　output　stage　can　be　eliminated　and　the　power　efficiency　of　the　stimulator　can　be　improved.　In　this　work,　the　exponential　current　generation　circuit　is　improved　to　realize　longer　duration　for　stimulation　pulse.　In　addition,　a　charge　balancing　technique　is　used　to　minimize　the　residual　charge　during　stimulation.　The　stimulator　IC　is　implemented　in　a　180-nm　CMOS　process,　occupying　a　core　area　of　1.93　mm(2).　The　simulation　results　show　that　maximum　power　efficiency　of　the　output　stage　reaches　90%　and　the　maximum　stimulation　duration　has　been　increased　by　3　times　compared　to　previous　work.　The　results　also　show　that　the　short-time　pulse　insertion　circuit　for　charge　balancing　can　maintain　the　electrode　voltage　within　a　safe　range　(V-ref　+/-　50　mV),　and　the　maximum　residual　charge　in　a　single　cycle　is　only　84　pC.