#### ckck20

##### Member level 1

We have Vin=23-25V , Vz=12.4, Izmin=10mA, Izmax=250mA and the load current IL=20-400mA. (Suppose that instead the RL we have a current source).

For simplicity we don't care about RL or about the zener resistance.

What we want to find is the limits (min,max) for the resistance R(the min is my problem).

My thought:

The Rmax should allow with Vinmin the max IL.

Therefore Rmax=(Vinmin-Vz)/(Izmin+ILmax)=25.8 Ohms

Similarly with Rmin

Rmin=(Vinmax-Vz)/(Izmax+ILmin)=46.7 Ohms

Obviously something is wrong. Something that you hopefully point out.

Thanks in advance.