Clear[vgs, ut,  A, ij, n];
"current in weak inversion";

ans=Solve[{ij==A Exp[(vgs/(n ut))]},{vgs},Reals]

FullSimplify[i1toi2=A ((Exp[(vgs1/(n ut))])/(A Exp[(vgs2/(n ut))]))]

"vg1-vgs2=vout";
Simplify[Solve[{(i1/i2)==(E^(vout/(n ut))),i1+i2==2 if},{i1,i2}]]

"Krummenacher- sum in right branch is if+idis = i1 (idis is supplied through CL),
sum in left branch is if= i2+idis (current through M3 constant because of big Ck)";
FullSimplify[Solve[{if+idis==((2 (E^(vout/(n ut))) if)/(1+(E^(vout/(n ut))))),if==((2 if)/(1+(E^(vout/(n ut)))))+idis},{idis}]]
Solve[{if+idis==((2 (E^(vout/(n ut))) if)/(1+(E^(vout/(n ut))))),if==((2 if)/(1+(E^(vout/(n ut)))))+idis},{idis}]