A B D 3RP2、RP1 R 2R 2R IF RE REF REF R REF REF REF 2R 4 REF 4R REF REF REF REF 8 8R 16 16RR V I I R V I I R V I I R V I I REF REF REF REF REF REF REF REF 16 16 1 8 8 1 4 4 1 2 2 1 1 0 3 2 = = = = = = = = 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 IREF i F i S3 S2 S1 S0 d3 d2 d1 d0 +VREF uo － + A B C D R V I REF REF =