+VREF REF 73 2R 7 8R6 设R=R/2 S RE o uo d i=Iodo+I d+1d,+I3d VE】+d十kEFd2+ 8R 4R R d,2+d,2+d-2'+d2) 23R 。=-Rip= d22+d,22+d2+d。2） 24 R 2R 4R 8R RF I 1 I I 3 I 2 0 I REF i F i S3 S2 S1 S0 d3 d2 d1 d0 +VREF uo － + ( 2 2 2 2 ) 2 8 4 2 0 0 1 1 2 2 3 3 3 0 1 2 3 0 0 1 1 2 2 3 3 =  +  +  +  = + + + = + + + d d d d R V d R V d R V d R V d R V i I d I d I d I d REF REF REF REF REF ( 2 2 2 2 ) 2 2 0 0 1 1 2 2 3 o 4 3 = − = −  = − d  + d  + d  + d  V i R u R i REF F F 设RF=R/2