Concept:An ideal diode has zero forward threshold voltage. Practical silicon and germanium diodes require forward voltages approximately equal to their built-in barrier potentials to conduct significant current.
Formula:$$V_{F,\text{ideal}} = 0.0\text{ V}, \quad V_{F,\text{Si}} \approx 0.7\text{ V}, \quad V_{F,\text{Ge}} \approx 0.3\text{ V}$$
Solution:- An ideal diode has no threshold voltage (\( V_F = 0.0\text{ V} \)).
- A practical silicon diode has a forward threshold of \( \approx 0.7\text{ V} \).
- A practical germanium diode has a forward threshold of \( \approx 0.3\text{ V} \).
Why other options are incorrect:- Option A: This scrambles the forward voltage values.
- Option C: 1.1 V is the bandgap of silicon in eV, not an ideal diode threshold.
- Option D: This swaps the values for silicon (0.7 V) and germanium (0.3 V).
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.