Question

A 8 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be ____ Ω.

Answer 1

R will be minimum when RL is infinitely large, so
RZener=$\frac{8}{25×10^{−3}}$
RZener=320 Ω
So, $\frac{R}{R_{Zener}}=\frac{12}{8}$
R=$\frac{12}{8}$×320
R=480 Ω
So, the answer is 480 Ω.