1. The problem statement, all variables and given/known data Create a 15V regulated power supply capable of providing a maximum load current of 25 mA. Circuit looks like this: http://i.imgur.com/fMtscbG.png?1 ILmax (maximum load resistance) = 25mA Izt (test current) = 20mA Izk (knee current) = 25mA rz = 11 Ω Vz (nominal zener voltage at Izt)= 15V Vs = 39V[itex]\pm[/itex]1V RL = 1kΩ R = ? 2. Relevant equations Vz = Vz0 + rz*Iz 3. The attempt at a solution Vz=14.78 V To find R I need to determine the total current in the circuit. I'm not sure whether it's correct to assume that the current Iz=0 when IL=25 mA. Since the load voltage is 25V when IL is at its max I thought it meant that the zener diode would be disconnected.