=l3+2+1+=D3+AD2+ED1+E R 2R 4R 8R R -2+—+ D,+22D+2D,+2D R 2 2022222R 取=尽2,则 U。=-I·Rn=-I R U F pD2+2D2+2D1+2D] 张 2 孝取RF=R/2，则   0 0 1 1 2 2 3 3 3 3 0 2 1 1 2 0 3 3 2 1 0 3 2 1 0 2 2 2 2 2 2 2 2 2 2 4 8 D D D D R D D D D U R U D R U D R U D R U D R U I I I I I R R R R R R = + + +       = + + + = + + + = + + +   0 0 1 1 2 2 3 3 4 2 2 2 2 2 2 D D D D R U U I R I R O = −  F = −  = − + + +