BEE BEE Bachelor of Electrical Engineering Semiconductor Devices and Electronics Questions and Answers 2 — Questions and Answers
Question 1: What is the primary function of a Zener diode in a circuit?
- Voltage regulation (Correct answer)
- Signal amplification
- Current amplification
- Frequency modulation
Correct answer: Voltage regulation
A Zener diode operates in reverse breakdown to maintain a constant voltage across its terminals, making it ideal for voltage regulation.
Question 2: In a MOSFET, what does the threshold voltage (Vth) represent?
- The minimum gate-to-source voltage needed to create a conducting channel (Correct answer)
- The maximum drain-to-source voltage before breakdown
- The voltage at which the device enters saturation
- The forward voltage drop across the gate oxide
Correct answer: The minimum gate-to-source voltage needed to create a conducting channel
The threshold voltage is the minimum gate-to-source voltage required to form an inversion layer and create a conductive channel between source and drain.
Question 3: Which semiconductor material has a bandgap energy of approximately 1.12 eV at room temperature?
- Silicon (Correct answer)
- Germanium
- Gallium arsenide
- Silicon carbide
Correct answer: Silicon
Silicon has a bandgap energy of approximately 1.12 eV at 300 K, which is fundamental to its widespread use in electronics.
Question 4: What phenomenon causes the collector current in a BJT to increase slightly with increasing collector-emitter voltage in the active region?
- Early effect (Correct answer)
- Avalanche multiplication
- Thermal runaway
- Kirk effect
Correct answer: Early effect
The Early effect (base-width modulation) causes the effective base width to narrow as VCE increases, slightly increasing collector current.
Question 5: In a p-n junction, what is the built-in potential primarily caused by?
- Diffusion of carriers across the junction creating an electric field (Correct answer)
- External bias applied to the junction
- Recombination of electrons and holes
- Thermal generation of electron-hole pairs
Correct answer: Diffusion of carriers across the junction creating an electric field
The built-in potential arises from carrier diffusion across the junction, which creates a depletion region and an internal electric field that opposes further diffusion.
Question 6: What is the main advantage of a CMOS inverter compared to an NMOS-only inverter?
- Near-zero static power dissipation (Correct answer)
- Higher switching speed
- Smaller chip area
- Lower threshold voltage
Correct answer: Near-zero static power dissipation
CMOS inverters have near-zero static power dissipation because one of the two transistors is always off in either logic state, preventing a direct path from supply to ground.
BEE BEE Bachelor of Electrical Engineering Semiconductor Devices and Electronics Questions and Answers 2
What is the primary function of a Zener diode in a circuit?