6-16 U0=lc3(R3‖R‖R),U=l3R3 6-17 RI (a a R R8+Rs+r3 6)1 R Uf e u f f C L U U U I R R R U I R A      = = = 0 3 8 9 3 3 0 ( || || ), , 6-16 6-17 S f ufb S S i e C f ufa U U A R U I R U b I I R R R R R R I U U a A       = − = = + + = = 0 1 0 4 3 8 5 3 8 7 4 0 ( ) , , （ ）