Physics

Semiconductors and Diodes

457 Questions

Semiconductors and diodes form the foundation of modern electronics, covering topics like intrinsic carrier concentration and Zener breakdown. Questions often explore the characteristics of bipolar junction transistors (BJT) and the properties of doped silicon materials. This topic is crucial for physics and electronics engineering competitive exams.

Zener diode breakdownBJT circuit analysisIntrinsic carrier concentrationDoping in semiconductorsEmitter follower circuit

Semiconductors and Diodes Questions

Multiple choice

The fermi level in a p-semiconductor lies close to

  1. The top of the valence band

  2. The top of the conduction band

  3. The bottom of the valence band

  4. The bottom of the conduction band

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As we increase the concentration, fermi level goes downwards from the middle, which will be the top of the valence band. At high temperature, p-type and n-type act as intrinsic semiconductors.

Multiple choice

A small increase in the collector reverse bias will cause

  1. A large increase in the emitter current

  2. A large increase in the collector current

  3. A large decrease in the collector current

  4. A very small change in collector reverse saturation current

  5. None of these

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

the reverse saturtaion current is not affected by it. 

Multiple choice

A transistor is said to be in a quiescent stage when

  1. The emitter junction bias is just equal to the collector junction bias

  2. No currents are flowing

  3. No signal is applied to the input

  4. It is unbiased

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Q-point can be found out while there is no input signal.

Multiple choice

Early effect in BJT refers to

  1. Avalanche breakdown

  2. Thermal runway

  3. Base narrowing

  4. Zener breakdown

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The early effect is the variation in the width of the base in a bipolar junction transistor (BJT) due to a variation in the applied base-to-collector voltage.

Multiple choice

Conduction electrons in a semiconductor have higher mobility than holes because they

  1. Have negative charge

  2. Are lighter

  3. Experience collisions less frequently

  4. Need less energy to move them

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The mobility is inversely proportional to the effective mass and the effective mass of a hole is much higher than that of an electron. Thus, the mobility of an electron is higher than that of a hole.

Multiple choice

CMOS means

  1. complementary metal oxide semiconductor

  2. costly metal oxide semiconductor

  3. complementary metal oxygen semiconductor

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

CMOS stands for Complementary Metal Oxide Semiconductor, a technology used for constructing integrated circuits.

Multiple choice

MOS is a ____ transistor.

  1. bipolar

  2. tripolar

  3. unipolar

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

MOS transistors (like MOSFETs) are unipolar devices, meaning their operation depends on only one type of charge carrier (either electrons or holes).

Multiple choice

PMOS means

  1. p channel mos

  2. p complement mos

  3. carrier mos

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

PMOS stands for P-channel Metal Oxide Semiconductor, which uses p-type charge carriers for conduction.

Multiple choice

The addition of pentavalent impurity to a semiconductor creates ______.

  1. holes

  2. free electrons

  3. minority electrons

  4. majority electrons
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pentavalent impurities have five valence electrons. When added to a semiconductor like silicon, four electrons form covalent bonds, leaving one extra electron free to conduct electricity, creating an n-type semiconductor with majority electrons.

Multiple choice

Which of the following is the fastest switching device?

  1. BJT

  2. JFET

  3. MOSFET

  4. Triode
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

MOSFETs are voltage-controlled devices with very high input impedance, allowing them to switch states much faster than current-controlled devices like BJTs. This makes them ideal for high-frequency digital and power switching applications.