function y=gvc(vc1,R)
   R1=300;
   R2=300;
   R3=1.2*10^3;
   R4=3.3*10^3;
   R5=3.3*10^3;
   R6=47*10^3;
   R7=47*10^3;
   Vd=0.6;
   Vc=9;
   Vb=Vc*R5/(R5+R7);
   E=Vb+Vd;
   m0=1/R5-R2/(R1*R3);
   m1=-R2/(R1*R3);
   a=m1*R;
   b=m0*R;
    if abs(vc1)<=E
       y=a*vc1;
    elseif vc1>E
       y=b*vc1+E*(a-b);
    else y=b*vc1-E*(a-b);
    end