Tag: electronic devices

Questions Related to electronic devices

The avalanche breakdown in p-n junction is due to

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

  1. shift of Fermi level.

  2. cumulative effect of conduction band electron.

  3. widening of forbidden gap.

  4. high impurity concentration.

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Correct Option: B
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.

A Zener diode

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

  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.

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Correct Option: B
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.

The current flow in a Zener diode is mainly due to

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

  1. thermally generated charge carriers

  2. minority charge carriers

  3. collision generated charge carriers

  4. ions

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Correct Option: C
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

Zener diode works on

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

  1. zero bias

  2. reverse bias

  3. forward bias

  4. infinite bias

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Correct Option: B
Explanation:

We know that zener diode works on the reverse bias. When the reverse bias is equal to the break-down voltage, the voltage across the zener remains almost constant and the current increases rapidly.

Zener diode acts as a/an

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

  1. oscillator

  2. regulator

  3. rectifier

  4. fliter

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Correct Option: B
Explanation:

Zener diode is used to supply constant voltage in voltage regulator circuit hence option (b) is correct.

A zener diode can be used as 

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

  1. oscillator .

  2. voltage regulator.

  3. rectifier.

  4. transformer.

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Correct Option: B

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

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

  1. increased, decrease

  2. increased, increase

  3. decreased, increase

  4. decreased, decrease

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Correct Option: B
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.

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

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

  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.

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Correct Option: A
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.

Zener-diode is used in.

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

  1. Amplification

  2. Rectification

  3. Oscillator in producing oscillations

  4. Volatge regulation

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Correct Option: D
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. 

Zener diode is a voltage regulation device.

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

  1. True

  2. False

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Correct Option: A
Explanation:

True. 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.