Let us consider the VCVS of Fig. 3.11, redrawn as shown in Fig. 4.10. The reference node is shown as grounded, so that the voltages v1 and v2 of Fig. 3.11 are now node voltages, as shown. Since the voltage is zero between the input terminals of the op amp and the currents are zero into the input terminals, we see that v3=v1 and that node equation written at node v3 is