$*2\mathrm{.}78$ The two circuits in Fig. P$2\mathrm{.}78$ are intended to function as voltage$-$to$-$current converters; that is$,$ they supply the load impedance $Z_L$ with a current proportional to $v_J$ and independent of the value of $Z_L.$ Show that this is indeed the case, and find for each circuit $i_o$ as a function of $v_l.$ Comment on the differences between the two circuits.

Express $v_o$ in terms of $v_{II}$ and $v_{I2}.$