Discussion
The threshold voltage of a MOSFET can be lowered by
1. using a thinner gate oxide
2. reducing the carrier concentration in the substrate
3. increasing the carrier concentration in the substrate Of these statements :
Answer: B
Statements 1 and 2 are correct. The threshold voltage of a MOSFET is
\[ V_{T} = V_{FB} + 2\phi_{F} + \frac{Q_{d}}{C_{ox}} \]
where \(Q_{d} = \sqrt{2\epsilon q N_{A}(2\phi_{F})}\) is the depletion charge.
A thinner gate oxide raises \(C_{ox}\) and lowers the last term, so statement 1 is right. Reducing the substrate carrier concentration lowers the depletion charge and also lowers \(2\phi_{F}\), so \(V_{T}\) falls and statement 2 is right. Increasing the concentration does the opposite and raises \(V_{T}\), so statement 3 is wrong. That rules out the options that contain 3.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development