2加法器 L=L+=0 R =0 l/R1+u12/R2+ui3/R3 R3 IR =-(Rr/R11+Rr/R212+Rr/R3i3) 比例加法器:y=a1x1+a2x2+a33,符号如下图:2. 加法器 比例加法器：y =a1x1+a2x2+a3x3，符号如下图： ui1/R1+ ui2 /R2+ ui3 /R3 =-uo /Rf uo= -(Rf /R1 ui1 +Rf /R2 ui2+Rf /R3 ui3) u -= u +=0 i-=0 + _ uo _ +  + R2 Rf i- u + u - R1 R3 ui1 ui2 ui3 x1 a1 a2 a3 -1 x2 -y y x3