Match Column I with Column II.
| Column I | Column II |
| 1. Threshold (cut-in) voltage of a Ge diode | A. 0.7 V |
| 2. Threshold (cut-in) voltage of a Si diode | B. 0.2 V |
| 3. Energy gap of Ge | C. 1.1 eV |
| 4. Energy gap of Si | D. 0.7 eV |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1-B, 2-A, 3-D, 4-C
The threshold (cut-in) voltage is the forward voltage beyond which the diode current rises sharply. The energy gap is the gap between the valence band and the conduction band of the material.
1. Threshold (cut-in) voltage of a Ge diode — This matches (B) 0.2 V. A germanium diode passes almost no current until the forward voltage crosses about 0.2 V.
2. Threshold (cut-in) voltage of a Si diode — This matches (A) 0.7 V. A silicon diode needs about 0.7 V before its current increases significantly.
3. Energy gap of Ge — This matches (D) 0.7 eV. Germanium has the smaller gap of the two, about 0.7 eV.
4. Energy gap of Si — This matches (C) 1.1 eV. Silicon has a gap of about 1.1 eV.
NCERT (2026-27):
p-n Junction Diode under Reverse Bias – “… After the characteristic voltage, the diode current increases significantly (exponentially), even for a very small increase in the diode bias voltage. This voltage is called the threshold voltage or cut-in voltage (~0.2V for germanium diode and ~0.7 V for silicon diode).”
Extrinsic Semiconductor – “… The difference in the resistivity of C, Si and Ge depends upon the energy gap between their conduction and valence bands. For C (diamond), Si and Ge, the energy gaps are 5.4 eV, 1.1 eV and 0.7 eV, respectively.”