A B D R R REF 2R 2R 2R 2R 2R -lodo+ld,+ 0+-d1+-d2+ REF 16 4 2 R =AE(d3·23+d2·2+ad1·21+d0·2°) 24R REF u=AFLF Ri= 4n(a3·23+a222+d1·21+dn.20 24R( 2 2 2 2 ) 2 ) 2 1 4 1 8 1 16 1 ( 0 0 1 1 2 2 3 4 3 0 1 2 3 0 0 1 1 2 2 3 3 =  +  +  +  = + + + = + + + d d d d R V R V d d d d i I d I d I d I d REF REF ( 2 2 2 2 ) 2 0 0 1 1 2 2 3 o 4 3 = − = − = − d  + d  + d  + d  R V R u R i R i REF F F F F R R R 2R 2R 2R 2R 2R RF I 1 I'1 I' I'3 2 I'0 I I 3 I 2 0 I REF i F i S3 S2 S1 S0 d3 d2 d1 d0 +VREF uo － + A B C D