Since there is no independent source in the network VTH = O V To find RTh apply : A current source of 1 A across A and B. Apply KCL at node n1 Apply KCL at node Vn2 Vn1 = 2Vx put in (i) ∴ Vn2 = 4vx put in (ii) 100 + Vx = 2Vx 100 = Vx ∴ Vn2 = 4Vx = 400 V ∴ .