4.68 Using the exponential diode characteristic, show that for vs and v, both greater than zero, the circuit of Fig. 4.23(a)has the transfer characteristic v_{o}=v_{s}-v_{D}\left(\text { at } i_{D}=1 \mathrm{~mA}\right)-V_{T}

\ln \left(v_{o} / R\right) where vs and v, are in volts and R is in kilohms. Note that this relationship can be used to obtain the voltage transfer characteristic vo vs. vs by finding v, corresponding to various values of