Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

The avalanche breakdown in p-n junction is due to

  1. shift of Fermi level.

  2. cumulative effect of conduction band electron.

  3. widening of forbidden gap.

  4. high impurity concentration.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The avalanche breakdown in p-n junction is due to cumulative effect of conduction band electron. In reverse bias, due to applied electric field, electrons acquire enough energy to free more electron bound to the atom. The abundant number of electron-hole pairs are created for conduction, this is cumulative effect.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

A Zener diode

  1. is a lightly doped junction diode.

  2. heavily doped junction diode.

  3. is either p-type or n-type.

  4. has no p-n junction.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reverse breakdown voltage depends on doping of the diode. Hence, in the Zener diode the heavy doping of its p-n junction is done. The depletion region formed in the diode is very thin ($<1\ m$) and the reverse bias voltage of about $5\ V$ which is less than ordinary diode.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

The current flow in a Zener diode is mainly due to

  1. thermally generated charge carriers

  2. minority charge carriers

  3. collision generated charge carriers

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

When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to avalanche breakdown. Avalanche breakdown occurs in reverse bias when the applied voltage is high enough, the free electron may move fast enough to knock other electrons free, creating more free-electron-hole pairs (i.e., more charge carriers), increasing the current. Thus, the current flow in a Zener diode is mainly due to collision generated charge carriers

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

At breakdown voltage, the rate of creation of hole-electron pairs is _____  leading to the _______  in current. 

  1. increased, decrease

  2. increased, increase

  3. decreased, increase

  4. decreased, decrease
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When the reverse voltage across a diode is very large, the valance electrons become free due to applied high electric field and get enough acceleration to make other electrons free, thus create a lot of electron-hole pairs in a short time. As the number of charge carriers increases, current also increases.

Therefore, at breakdown voltage, the rate of creation of hole-electron pairs is increased leading to the increase in current.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

Which of these is the best description of a Zener diode ?

  1. It is a constant voltage device.

  2. It operates in the reverse region.

  3. It is a constant current device.

  4. It works in forward region.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Zener diode is a p-n junction diode working in the breakdown region. It is used as a voltage regulator/stabilizer to provide a constant voltage from a source whose voltage may fluctuate over a wide range.

Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

Zener-diode is used in.

  1. Amplification

  2. Rectification

  3. Oscillator in producing oscillations

  4. Volatge regulation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 A voltage regulator circuit can be designed using a zener diode to maintain a constant DC output voltage across the load in spite of variations in the input voltage or changes in the load current.