上图的关系式: 2=(+B)R2=(4+B)cR1=A1 R, A=(+B)=0 Ay (1+B)R v.1 n+(1+B)Rbe i o v = v − v f o v = v ( ) L v b e b e b e o e L b L R A v r v v = i R = + i R = + = ' ' ' (1  ) 1  be o be L v v v r R A = + = ' (1  ) 上图的关系式： v v i o vf A A v v A + = = 1 ( ) ' ' 1 (1 ) be L L vf r R R A   + + + =