R (6)同相求和运算 RI R R F A=1+ R f R 取R1/R2=Rp/Rr R F R R ul=Auu+=(1+)( u RI+R Ri+R 2) R 2 2 当R1=R2时,u o÷1 R F (1+ )(un+u12) 2 R14 (6) 同相求和运算： Au= RF Rf 1+ uo = Au u+ =( )( + ) RF Rf 1+ R2 R1 + R2 ui1 R1 R1 + R2 ui2 取R1 //R2=RF //Rf 当R1 = R2 时, uo = ( )(ui1 + ui2) RF Rf 1+ 1 2 Rf RF  + + ui1 R1 uo R2 ui2 - u+ _ +  +  RF Rf RP ui uo