Question

Find the minimum load resistance which can be used for the zener diode as shown in figure. Given, $V_Z=10V,R_Z=0\Omega ,R=450\Omega ,I_Z\left(min\right)=2mA$ and $I_Z\left(max\right)=60mA$

• A. $0\Omega$
• B. $333.3\Omega$
• C. $31.95\Omega$
• D. $319.5\Omega$

Answer 1

The correct option is D $319.5\Omega$

Apply Kirchoff's voltage law to loop including battery and zener diode.

$⟹25-iR-V_Z=0$

$⟹i=33.3mA$

Thus this current can be separated into zener diode branch and load resistance branch.
Hence $I_{RL}+I_Z=33.3mA$
$⟹I_{R{L}_{max}}=33.3mA-I_{Z_{min}}=33.3mA=31.3mA$

Hence minimum load resistance which can be used=$\frac{V_{RL}}{I_{R{L}_{max}}}$

$=\frac{V_Z}{I_{R{L}_{max}}}=\frac{10}{0.0313}\Omega$
$=319.5\Omega$