Concept:A Zener diode is designed to operate in reverse breakdown, where its terminal voltage remains virtually constant at \( V_Z \) over a wide range of reverse currents, making it ideal for voltage regulation.
Formula:$$V_{\text{out}} = V_Z = \text{constant} \quad (\text{for } I_{Z,\text{min}} < I_Z < I_{Z,\text{max}})$$
Solution:- In reverse breakdown, the slope of the I-V curve is nearly vertical (very low dynamic impedance \( r_z \)).
- This allows the Zener diode to maintain a stable reference voltage despite fluctuations in supply voltage or load current.
Why other options are incorrect:- Option A: In forward bias, a Zener diode behaves like an ordinary silicon diode (\( V_F \approx 0.7\text{ V} \)) without voltage regulation.
- Option B: In an unbiased state, the diode does not conduct or regulate voltage.
- Option D: Below breakdown, the diode only passes a tiny leakage current and cannot regulate voltage.
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