A zener diode regulator in the figure is to be designed to meet the specifications: $I_{L}=10 \mathrm{~mA}$, $\mathrm{V}_{0}=10 \mathrm{~V}$ and $\mathrm{V}_{m}$ varies from $30 \mathrm{~V}$ to $50 \mathrm{~V}$. The zener diode has
$V_{z}=10 \mathrm{~V}$ and $I_{z k}$ (knee current) $=1 \mathrm{~mA}$. For satisfactory operation.
- $R \leq 1800 \; \Omega$
- $2000 \; \Omega \leq R \leq 2200 \; \Omega$
- $3700 \; \Omega \leq R \leq 4000 \; \Omega$
- $\mathrm{R}>4000 \; \Omega$