CC R G2 图P6-12 ≌m(RD‖R2),R2=b+(1+B)R ul 1+omR A12=- BR +(1+B)Rg R (Rs+R) R. Uo=l R,+R、+R Rtr+r Uf u f f S L L S f S C f S L L f C u u u b e E L u D i i b e E m S m u U U A R R R R R R R U I R R R R U I A A A r R R A R R R r R g R g A     = + + + = + + = = + + − = = + + + − = 0 2 0 2 2 1 2 1 2 2 , ( ) , , (1 ) ( || ), (1 ) 1   