Physics

Semiconductors and Diodes

461 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

Which of the folowing possesses an ability to control a very large signal on one of its terminals by using a small signal applied between another pair of terminals?

  1. Insulators

  2. Dopants

  3. Semiconductors

  4. Conductors

  5. Transistors
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit.

Multiple choice

In solid-state electronics, which of the following can be used in proper type and amount to produce p-type semiconductors and n-type semiconductors that are essential for making transistors and diodes?

  1. Power

  2. Pressure

  3. Dopants

  4. Forward bias

  5. Heat
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance (in very low concentrations) in order to alter the electrical properties or the optical properties of the substance.

Multiple choice

A PN junction diode is connected to a battery of emf 5.5 V and external resistance 5.1 kΩ. The barrier potential in the diode is 0.4 V. The current in the circuit is

  1. 0.07843 mA

  2. 1.07 mA

  3. 927.27 A

  4. 28050 A

  5. 12750 A
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Out of 5.5 volts, 0.4 volt (barrier potential) is dropped across the forward biased diode and the remaining 5.1 volts appears across the 5.1 kΩ resistance. So, the current through the resistance is (5.5 V /5.1kΩ), which is equal to 1.07 mA

Multiple choice

What causes the depletion region?

  1. Doping

  2. Diffusion

  3. Barrier Potential

  4. Ions

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

Diffusion of electrons and holes causes the depletion region.

Multiple choice

Consider the following statements over Reverse bias voltage, (N region positive w.r.t. the P region) (a) It increases the potential barrier. (b) It decreases the space charge width. (c) It decreases the magnitude of electric field. Which of the above statements are correct?

  1. Only (a) and (b)

  2. Only (b) and (c)

  3. Only (a)

  4. All (a), (b) and (c)

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

Statement (a) is correct: It increases the potential barrier. Statement (b) is wrong: It increases the space charge width and statement (c) is wrong: It increases the magnitude of electric field.

Multiple choice

Consider the following statements regarding half-wave rectifier: (a) Diode converts ac input voltage to a pulsed dc output voltage (b) Diode introduces a 0.6V drop so o/p peak is 0.6V smaller than the i/p peak (c) The o/p frequency is different than the i/p frequency Which of the above statements is/are true?

  1. Only (a)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All the above

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

Statement (a) is true.  Diode converts ac input voltage to a pulsed dc output voltageStatement (b) is true: Diode introduces a 0.6V drop so o/p peak is 0.6V smaller than the i/p peak.Statement (c) is false: The o/p frequency is same as the i/p frequency.

Multiple choice

Consider the following statements regarding Photo - diodes: (a) Photodiode is a 4 lead semiconductor device that transforms light energy to electric current (b) Photodiodes have very linear light v/s current characteristics (c) Photodiodes are less sensitive than photo-resistor Which of the above statements are true?

  1. Only (a) and (c)

  2. Only (a) and (b)

  3. Only (b)

  4. Only (c)

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

Statement (a) is wrong. Photodiode is a 2 lead semiconductor device that transforms light energy to electric current. Statement (b) is correct. Photodiodes have very linear light v/s current characteristics. Statement (c) is wrong. Photodiodes are more sensitive than photo-resistor.

Multiple choice

Consider the following statements regarding JFET: (a) Junction field effect transistors like BJTs are three lead semiconductor devices (b) JFETs are normally off when VG - VS = 0 (c) Unlike BJTs, JFETs do not require a bias current and are controlled by using only a voltage Which of the above statements is/are true?

  1. Only (a) and (c)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All of the above

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

Statement (a) is true. Junction field effect transistors like BJTs are three lead semiconductor devices. Statement (b) is false. JFETs are normally ON when VG - VS = 0. Statement (c) is true. Unlike BJTs, JFETs do not require a bias current and are controlled by using only a voltage.

Multiple choice

Consider the following statements regarding Photo-transistor: (a) Phototransistor is a light sensitive transistor (b) When the light sensitive surface at the base is exposed to light, the collector-emitter pair of the BJT does not conduct (c) When the light sensitive surface at the base is kept in darkness, a small amount of current flows from the base to the emitter. The small base-emitter current controls the larger collector-emitter current Which of the above statements are false?

  1. Only (a) and (c)

  2. Only (a) and (b)

  3. Only (b) and (c)

  4. All of the above

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

Statement (a) is true. Phototransistor is a light sensitive transistor.Statement (b) is false. When the light sensitive surface at the base is kept in darkness, the collector-emitter pair of the BJT does not conduct.Statement (c) is false. When the light sensitive surface at the base is exposed to light, a small amount of current flows from the base to the emitter. The small base-emitter current controls the larger collector-emitter current.