6. [10%] Fig. 5 shows the circuits illustration of full-wave rectifier with four constant-voltage diodes \( (V{D,ON} = 0.7\mathrm{V}) \). Plot the \( V{in} / V{out} \) characteristics curve. (Hint: \( V{in} \) as \( x \)-axis and \( V_{out} \) as \( y \)-axis).