Since I learned about the diode devices so long ago, I have never been able to answer one problem. If we have a zener diode with 5,6v treshold voltage and a transistor with 0,7v treshold voltage, and we connect the negative end of the diode and the base of the npn transistor to a base ressistor directly, then how to find what the current through each of them will be? It's easy to solve this if they were resistors, but the only thing you know about them is that they have some turn on voltage, so I can't use Ohm's law. Except if I gi with the internal ressistance of the devices, but that is too far away from the whole thing and sounds complicated and out of place. Forgot to mention that the emitter is hold at constant 5volts so the transistor can't short the base ressistor. It's confusing me, there is nothing I can hook up to to figure out the zener current or the base current. Sure the zener have some minimum turn on current, but how do I know that this current wont be more. Is it load dependent? Maybe the five volts through the load give some emitter current and thus a certain base current and you can substract that base current from the whole current through the base ressistor to find the zener current Iz = Is-Ib ? I don't know, it's almost like they act by a coincidence, but i'm pretty sure it's load dependant.