D4.19 Design the circuit of Fig. E4.19 so that VO = 3V when IL = 0, and VO changes by 20 mV per 1 mA of load current.
(a) Use the small-signal model of the diode to find the value of R.
(b) Specify the value of IS of each of the diodes.
(c) For this design, use the diode exponential model to determine the actual change in VO when a current IL = 1 mA is drawn from the regulator.