**4.52 In Problem 4.51 we investigated the operation of the circuit in Fig. P4.51 for small input signals. In this problem we wish to find the voltage-transfer characteristic (VTC) v O versus v I for −12V ≤ v I ≤ 12V for the case I = 1 mA and each of the diodes exhibits a voltage drop of 0.7 V at a current of 1 mA. Toward this end, use the diode exponential characteristic to construct a table that gives the values of: the current i O in the 10-k resistor, the current in each of the four diodes, the voltage drop across each of the four diodes, and the input voltage v I , for v O = 0, +1 V, +2 V, +5 V, +9 V, +9.9 V, +9.99 V, +10.5 V, +11 V, and +12 V. Use these data, with extrapolation to negative values of v I and v O , to sketch the required VTC. Also sketch the VTC that results if I is reduced to 0.5 mA. (Hint: From symmetry, observe that as v O increases and i O correspondingly increases, i D3 and i D2 increase by equal amounts and i D4 and i D1 decrease by (the same) equal amounts.)