Question

The 6 V zener diode shown below has zero zener resistance and a knee current of 5 mA. The minimum value of R, so that the voltage across it does not fall below 6 V is

• A. 0 $\Omega$
• B. 50 $\Omega$
• C. 80 $\Omega$
• D. 1.2 k$\Omega$

Answer 1

The correct option is C 80 $\Omega$


$I=\frac{10-6}{50}=80mA$

$I=I_Z+I_I=I_{z_{min}}+I_{L_{max}}$

$I_{Zmin}=5mA$

$80=5+I_{Lmax}$

$I_{Lmax}=75mA$

$I_{Lmax}=\frac{V_L}{R_{min}}$

$R_{min}=\frac{V_L}{I_{L_{max}}}=\frac{6}{75\times {10}^{-3}}=80\Omega$