Tag: special purpose diodes

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Questions Related to special purpose diodes

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

If the revers bias voltage applied  to a p-n junction diode is increased, its barrier capacitance would:

  1. increase

  2. decrease

  3. remain constant

  4. first increase then decrease
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Barrier capacitance, also known as transition or depletion capacitance, is inversely proportional to the width of the depletion region. Increasing the reverse bias voltage widens the depletion layer, which in turn decreases the barrier capacitance. Therefore, option B is correct.

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

In a zener diode, break down occurs in reverse bias due to

  1. Impact ionisation

  2. Internal field emission

  3. High doping concentration

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Zener breakdown occurs due to high electric fields (internal field emission) in heavily doped diodes, while avalanche breakdown occurs due to impact ionization. Both are mechanisms associated with reverse bias breakdown.

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

Two capacitors each having capacitance C and breakdown voltage V are joined in series. The capacitance and the breakdown voltage of the combination will be 

  1. 2 C and 2 V

  2. C/2 and V/2

  3. 2 C and V/2

  4. C/2 and 2 V.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

We know that the charge on a capacitor is 
$\begin{array}{l} Q=CV \\ C\propto \dfrac { 1 }{ V }  \\ in\, \, series\, \, combination \\ { C _{ net } }=\dfrac { { { C _{ 1 } }{ C _{ 2 } } } }{ { { C _{ 1 } }+{ C _{ 2 } } } }  \\ Hence, \\ { C _{ eq } }=\dfrac { C }{ 2 }  \\ { V _{ combination } }=2V \end{array}$

$\therefore$ option $D$ is correct.
Multiple choice zener diode special purpose diodes electronic devices semiconductor electronics: materials, devices and simple circuits physics

What is the order of the reverse saturation current before breakdown in a Zener diode

  1. ampere

  2. milli-ampere

  3. it depends on the applied voltage

  4. micro-ampere
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Before the breakdown voltage is reached, a Zener diode acts like a normal diode under reverse bias, where only minority carriers contribute to a very small leakage current. This reverse saturation current is typically on the order of microamperes, making option D correct.

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

Which of the following is/are true regarding  breakdown voltage of Zener diode?

  1. If the reverse bias voltage across a p-n junction diode is increased, at a particular voltage the reverse current suddenly decreases to a large value

  2. The holes in the n-side and the conduction electrons in the p-side are accelerated due to the reverse bias voltage.

  3. The voltage at which the rate of creation of hole-electron pairs is increased leading to the increased current is called avalanche breakdown

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Consider applying an external voltage to the junction with the the negative terminal connected to the P type material and the positive terminal connected to the N type material. For the P-N junction this would require injecting electrons into the P type material. These electrons would recombine with holes and therefore further deplete the majority charge carriers in the P type semiconductor. 


Also removing electrons from the N type material would obviously cause further depletion the free electrons (the majority charge carriers in the N type semiconductor). This causes a widening of the depletion layer and an increase in the charge at the junction which reinforces the barrier voltage to oppose the applied voltage. The net result is that when the P-N junction is reversed biased it blocks current flow.

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

Which of the following semi-conducting devices is used as voltage regulator?

  1. Zener diode

  2. LASER diode

  3. Photo diode

  4. Solar cell
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Zener diode is used as a voltage regulator device because the voltage across the zener diode in reverse bias is constant after reaching certain value i.e. breakdown voltage.

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

What is true about the breakdown voltage in a zener diode?

  1. It decreases when current increases.

  2. It destroys the diode.

  3. It equals the current times the resistance.

  4. It is approximately constant.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As the current in the zener diode increases, the voltage across the diode remains constant. This voltage will be equal to the zener breakdown voltage