Zener Diodes MCQ Quiz - Objective Question with Answer for Zener Diodes - Download Free PDF

Last updated on May 30, 2025

Latest Zener Diodes MCQ Objective Questions

Zener Diodes Question 1:

The IC 723 is primarily used as a ________.

  1. clamper
  2. clipper
  3. rectifier
  4. voltage regulator

Answer (Detailed Solution Below)

Option 4 : voltage regulator

Zener Diodes Question 1 Detailed Solution

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IC 723 as a Voltage Regulator

The IC 723 is primarily used as a voltage regulator. It is a versatile and reliable integrated circuit (IC) that is designed to provide stable and regulated voltage output. The IC 723 is widely used in various electronic applications due to its excellent performance characteristics and ease of use.

Additional Information
 Applications of IC 723

The IC 723 is used in a wide range of electronic applications where a stable and regulated voltage is required. Some common applications include:

  • Power supply circuits: The IC 723 is used in power supply circuits to provide a stable and regulated voltage output for various electronic devices and systems.
  • Battery chargers: The IC 723 is used in battery charger circuits to regulate the charging voltage and ensure safe and efficient charging of batteries.
  • Voltage reference circuits: The IC 723 can be used as a voltage reference in precision measurement and instrumentation applications.
  • Voltage regulators for microcontrollers: The IC 723 is used to provide a stable and regulated voltage supply for microcontrollers and other digital circuits.

Conclusion

In conclusion, the IC 723 is primarily used as a voltage regulator. Its versatility, stability, and ease of use make it an ideal choice for a wide range of electronic applications. The IC 723 provides a stable and regulated output voltage, making it suitable for power supply circuits, battery chargers, voltage reference circuits, and voltage regulators for microcontrollers.

Zener Diodes Question 2:

Which of the following statements is/are NOT correct regarding an IC 723?
S1: The output voltage ranges from 2 to 37 volts.
S2: The output current is up to 150 mA.

  1. Neither S1 nor S2
  2. Only S2
  3. Only S1
  4. Both S1 and S2

Answer (Detailed Solution Below)

Option 1 : Neither S1 nor S2

Zener Diodes Question 2 Detailed Solution

Explanation:

To determine the correctness of the given statements about the IC 723 voltage regulator, we need to understand the specifications and characteristics of the IC 723.

IC 723 Overview:

The IC 723 is a versatile voltage regulator IC used for both positive and negative voltage regulation. It can operate over a wide range of input voltages and can be configured for different output voltage ranges and current outputs. The IC 723 is known for its reliability and flexibility in various power supply designs.

Specifications of IC 723:

  • Output Voltage Range: The IC 723 can be configured to provide an output voltage range from 2 volts to 37 volts. This is achieved by adjusting the external components connected to the IC, such as resistors and capacitors.
  • Output Current: The IC 723 can deliver an output current of up to 150 mA when used in its basic configuration. However, with the addition of an external pass transistor, the output current can be increased significantly, depending on the specifications of the external transistor.

Analysis of Statements:

  • S1: The output voltage ranges from 2 to 37 volts.
  • S2: The output current is up to 150 mA.

Based on the specifications of the IC 723, we can analyze the correctness of the statements:

  • S1: This statement is correct because the IC 723 can indeed provide an output voltage range from 2 to 37 volts by adjusting the external components.
  • S2: This statement is also correct because the IC 723 can deliver an output current of up to 150 mA in its basic configuration. The output current can be increased with the use of an external pass transistor, but the statement specifies the basic configuration.

Conclusion:

Since both statements S1 and S2 are correct, the correct answer is option 1, which states that neither S1 nor S2 is incorrect.

Important Information:

The IC 723 is highly versatile and can be used in various voltage regulation applications. Here are some additional points to consider:

  • The IC 723 includes an internal reference voltage source, error amplifier, series pass transistor, and a current limiting circuit.
  • It can be used to design both linear and switching regulators.
  • The output voltage can be adjusted using external resistors connected to the voltage adjustment pins of the IC.
  • The IC 723 can operate with input voltages up to 40 volts, making it suitable for a wide range of power supply designs.
  • For higher current applications, an external pass transistor can be added to boost the output current capability of the IC.
  • Thermal protection and current limiting features enhance the reliability and safety of the IC 723 in various applications.

In conclusion, the IC 723 is a reliable and flexible voltage regulator IC suitable for a wide range of applications, offering an output voltage range of 2 to 37 volts and an output current of up to 150 mA in its basic configuration. Both statements S1 and S2 are correct, making option 1 the correct choice.

Zener Diodes Question 3:

The output voltage of an IC 7905 is _________.

  1. 15 V
  2. 5 V
  3. −15 V
  4. −5 V

Answer (Detailed Solution Below)

Option 4 : −5 V

Zener Diodes Question 3 Detailed Solution

The output voltage of an IC 7905 is −5 V.

Explanation:
The 79XX series (e.g., 7905, 7912, 7915) are negative voltage regulators.

7905 provides a regulated 5V output.

Similarly:

  • 7905 → −5V
  • 7912 → −12V
  • 7915 → −15V

Zener Diodes Question 4:

What is the primary characteristic of a Zener diode that distinguishes it from a regular diode?

  1. Sharp breakdown voltage and ability to regulate voltage 
  2. Low forward voltage drop
  3. High reverse breakdown voltage
  4. High forward current rating

Answer (Detailed Solution Below)

Option 1 : Sharp breakdown voltage and ability to regulate voltage 

Zener Diodes Question 4 Detailed Solution

Zener diode

06.11.2018.001..08

  • A Zener diode is a heavily doped semiconductor device that is designed to operate in the reverse direction.
  • Under the forward-bias condition, the zener diode works as a normal PN junction diode.
  • During the reverse-bias condition, when the voltage across the terminals of a zener diode reaches the zener Voltage (breakdown voltage), the junction breaks down, and the current flows from the cathode to the anode.
  • The primary characteristic that distinguishes a Zener diode from a regular diode is its ability to maintain a constant voltage in the reverse breakdown region. 
  • This is due to the Zener diode's designed doping, allowing it to conduct current when the reverse voltage reaches a specific value, known as the Zener voltage. This feature makes Zener diodes useful for voltage regulation and protection. 

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Zener Diodes Question 5:

A zener diode of voltage VZ (= 6V) is used to maintain a constant voltage across a load resistance RL (= 1000Ω) by using a series resistance Rs(= 100Ω). If the e.m.f. of source is E (= 9V), what is the power being dissipated in Zener diode ?

  1. 0.144 watt 
  2. 0.324 watt 
  3. 0.244 watt
  4. 0.544 watt
  5. 0.455 watt

Answer (Detailed Solution Below)

Option 1 : 0.144 watt 

Zener Diodes Question 5 Detailed Solution

Calculation:

Here, E = 9V; Vz = 6; RL = 1000Ω and Rs = 100Ω, 

Potential drop across series resistor

V = E − VZ = 9 − 6 = 3V

Current through series resistance RS is

I = V/R = 3/100 = 0.03 A

Current through load resistance RL is 

IL = VZ/RL = 6/1000 = 0.006 A

Current through Zener diode is

IZ = I − IL = 0.03 − 0.006 = 0.024 amp.

Power dissipated in Zener diode is

PZ = VZ IZ = 6 × 0.024 = 0.144 Watt

Thus, power dissipated in Zener diode is 0.144 Watt. Option 4 is correct.

Top Zener Diodes MCQ Objective Questions

Find the output voltage of the given network if Ein = 6 V and the Zener breakdown voltage of the Zener diode is 10 V.

F1 Koda Raju 12.4.21 Pallavi D2

  1. 4 V
  2. 0 V
  3. 10 V
  4. 6 V

Answer (Detailed Solution Below)

Option 2 : 0 V

Zener Diodes Question 6 Detailed Solution

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Concept: 

The working of the Zener diode is explained in the below figures.

F1 S.B 1.9.20 Pallavi D28 (1)

Calculation:

Given,

Zener voltage Vz = 10 V

Ein = 6 V ⇒ Ein < Vz

Hence zener will be reverse biased and get open-circuited.

Output voltage E0 = 0 V

The value of Iz shown in the given circuit is ________.

F2 Vilas Engineering 8.12.2022 D2

  1. 0.02 A
  2. 0.02 mA
  3. 0.08 mA
  4. 0.08 A

Answer (Detailed Solution Below)

Option 4 : 0.08 A

Zener Diodes Question 7 Detailed Solution

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Concept

The value of Zener current is given by:

\(I_Z=I_S-I_L\)

\(I_Z={V_S-V_Z\over R_S}-{V_Z\over R_L}\)

where, Iz = Zener current

Vz = Zener voltage

Vs = Source voltage

Rs = Source resistance

RL = Load resistance

Calculation

Given, Vz = 20 V

Vs = 30 V

Rs = 100 Ω = 0.1 kΩ 

RL = 1 kΩ

\(I_Z={30-20\over 0.1}-{20\over 1}\)

IZ = 100 - 20 mA = 0.08 A

Which of the following devices is used in voltage regulators and voltage limiters as a fixed reference voltage in the network?

  1. PIN diode
  2. Varactor diode
  3. Zener diode
  4. Tunnel diode

Answer (Detailed Solution Below)

Option 3 : Zener diode

Zener Diodes Question 8 Detailed Solution

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Zener Diode:

The Zener diode operates just like the normal diode when in the forward-bias mode, and has a turn-on voltage of between 0.3 and 0.7 V. However when connected in the reverse mode, which is usual in most of its applications, a small leakage current may flow and the voltage across it is kept constant.

V - I characteristic of Zener diode

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Zener as a Voltage Limiter:

F1 Ravi Ranjan 21.5.21 Pallavi D7
A resistor, R1 is connected in series with the Zener diode to limit the amount of current flowing through the diode and the input voltage Vin (Which must be greater than the Zener voltage) is connected across as shown in the image, and the output voltage Vout is taken across the Zener diode with Vout = Vz (Zener Voltage).

They are used as Voltage limiter and voltage regulator.

Varactor Diode is a type of diode whose internal capacitance varies with respect to the reverse voltage.
It is used in frequency modulation for FM transmitters and phase-locked loops.

Tunnel diode is a type of semiconductor diode that has effectively "negative resistance" due to the quantum mechanical effect called tunneling. They areused in oscillator circuits, and in FM receivers.

PIN diode is a diode where an intrinsic layer of high resistivity is sandwiched between the P and N-region of semiconductor material. They are used in attenuators, fast switches, photodetectors

In the circuit shown below 18 V Zener diode has zero Zener resistance and a knee current of 2 mA. The minimum value of R so that voltage across it does not fall below 18 V is:

F1 ShubhamB Madhuri 16.04.2021 D8

  1. 1000 Ω
  2. 500 Ω
  3. 9000 Ω
  4. 2000 Ω

Answer (Detailed Solution Below)

Option 1 : 1000 Ω

Zener Diodes Question 9 Detailed Solution

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Concept:

Zener diode as voltage regulator:

  • Zener diodes are used in circuits to maintain a fixed voltage across a load.
  • It breaks down at a specific voltage when it is reverse biased. This means that a Zener diode will stop a reverse current from flowing through it until the reverse voltage applied across it reaches a fixed value known as the breakdown voltage (Vz).
  • It maintains the voltage at its breakdown voltage as long as the supply voltage is above this value.

 

Zener Knee Current:

The reverse current flows through the Zener diode at the break-down voltage.

Calculations:

607946ff5227db3fd05f55b6 16333591844621

\(\rm \frac{{\left( {20 - 18} \right)}}{{100}} = {I_Z} + {I_R}\)

\(\rm \frac{2}{{100}} = {I_{zmin}} + {I_{R\left( {max} \right)}}\)

\(\rm 2 \times {10^{ - 2}} = 2 \times {10^{ - 3}} + \frac{18}{{{R_{min}}}}\)

\(\rm {R_{min}} = \frac{18}{{18 \times {{10}^{ - 3}}}} = 1000\ \Omega\)

F6 Vinanti Engineering 24.11.22 D20 Symbol represents the: 

  1. Tunnel diode 
  2. Zener diode
  3. Photo-emissive diode 
  4. Photo sensitive diode

Answer (Detailed Solution Below)

Option 2 : Zener diode

Zener Diodes Question 10 Detailed Solution

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Symbols of various diodes:

1.) PN junction diode

F6 Vinanti Engineering 24.11.22 D22

2.) Zener diode

F6 Vinanti Engineering 24.11.22 D20

3.) Tunnel diode

F6 Vinanti Engineering 24.11.22 D23

4.) Schottky diode

F6 Vinanti Engineering 24.11.22 D24

5.) Varactor diode

F6 Vinanti Engineering 24.11.22 D25

6.) Photodiode

F6 Vinanti Engineering 24.11.22 D26

For the Zener diode network shown in figure, determine the value of VL?

F1  Madhuri Engineering 24.06.2022 D26

  1. 16 V
  2. 6 V
  3. 10 V
  4. 26 V

Answer (Detailed Solution Below)

Option 3 : 10 V

Zener Diodes Question 11 Detailed Solution

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Concept:

Zener diode is a silicon semiconductor device that permits current to flow in either a forward or reverse direction. The diode consists of a special, heavily doped p-n junction, designed to conduct in the reverse direction when a certain specified voltage is reached.

Voltage Vz: The Zener voltage refers to the reverse breakdown voltage.

Current Iz (max.): Maximum current at the rated Zener voltage Vz.

Current Iz (min.): Minimum current required for the diode to break down.

Calculation:

Given;

Vz = 10 V

Open circuit the Zener diode to calculate the voltage appearing across the diode.

F1  Madhuri Engineering 24.06.2022 D27

Vx = 16 × 4.2/(4.2+1) = 12.92 V

As, Vx > V→ Zener diode will be in the breakdown region.

VL = VZ = 10 V

The 6 V zener diode shown in the figure has zero zener resistance and a knee current of 5 mA. The minimum value of R so that the voltage across it does not fall below 6 V is

F1 Shubham.B 21-01-21 Savita D4

  1. 1.2 k ohms
  2. 80 ohms
  3. 50 ohms
  4. 0 ohms

Answer (Detailed Solution Below)

Option 2 : 80 ohms

Zener Diodes Question 12 Detailed Solution

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Concept:

If load Resistance is varying then it is known as load Regulation.

Under load Regulation:

F1 Neha B 25.3.21 Pallavi D 4

IL max = IS – IZ min

IL min = IS – IZ max

Calculation:

F1 Neha B 25.3.21 Pallavi D 5

VZ = 6 V

IZ min = 5 mA

Since we want a constant 6 V across R

\({I_S} = \frac{{10 - 6}}{{50}} = \frac{4}{{50}} = 80\;mA\)

IL Max = IS – IZ min = 80 – 5

= 75 mA

\({I_L} = \frac{6}{R}\)

\(R = \frac{6}{{75 \;\times\; {{10}^{ - 3}}}} = 80\;{\rm{\Omega }}\)

When biased correctly, a Zener diode: 

  1. Acts as a fixed resistance 
  2. Has a constant voltage across it 
  3. Has a constant current passing through it
  4. Never overheats 

Answer (Detailed Solution Below)

Option 2 : Has a constant voltage across it 

Zener Diodes Question 13 Detailed Solution

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Zener diode:

  • A Zener diode is a heavily doped semiconductor device that is designed to operate in the reverse direction.
  • When the voltage across the terminals of a Zener diode is reversed and the potential reaches the Zener Voltage (knee voltage), the junction breaks down and the current flows in the reverse direction. This effect is known as the Zener Effect.
  • The Zener diode acts as a voltage regulator.

The device used for voltage regulator is

  1. schottky diode
  2. zener diode
  3. varactor diode
  4. tunnel diode

Answer (Detailed Solution Below)

Option 2 : zener diode

Zener Diodes Question 14 Detailed Solution

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The device used for the voltage regulator is a Zener diode

Voltage regulator:

It is used to regulate the voltage level. It generates a fixed output voltage that remains constant for any changes in load conditions or input voltage.

Zener diode:

06.11.2018.001..08

06.11.2018.001..09

06.11.2018.001..10

  • It is PN junction (silicon PN junction) diode and has a low specified reverse voltage which takes advantage of any reverse voltage applied to it.
  • Unlike a normal diode (Schottky diode, varactor diode, tunnel diode) that blocks any flow of current through itself when reverse biased.
  • From the I-V characteristics curve above voltage across the diode in the breakdown, the region is almost constant.
  • In the breakdown region, it can be used as a voltage regulator applications.

26 June 1

Schottky Diode:

  • The Schottky diode is a semiconductor formed by the junction of a semiconductor with metal. It has a low forward voltage drop and near-zero reverse recovery time hence used in very fast switching circuits.
  • Schottky barrier diode can be used as a low noise amplifier due to metal-semiconductor junction.

 

Tunnel diode:

  • A tunnel diode is a highly doped semiconductor diode.
  • The tunnel diode shows negative resistance when the voltage value increases by decreasing the flow of current. Tunnel diode works based on the tunnel Effect.

Tunnel diode is represented by the symbol

F1 P.Y Madhu 9.03.20 D10

Varactor Diode:

  • Varactor diode refers to the variable Capacitor diode, which means the capacitance of the diode varies linearly with the applied voltage when it is reversed biased.
  • Varactor diode is commonly used for Electronic tuning.

It is represented by a symbol of diode terminated in the variable capacitor as shown below:

hark3

The 6 V Zener diode shown in the figure has zero Zener resistance and a knee current of 5 mA. The minimum value of R so that the voltage across it does not fall below 6 V is

sonkar Q6

  1. 1.2 kΩ

  2. 80 Ω

  3. 50 Ω

  4. 0 Ω

Answer (Detailed Solution Below)

Option 2 :

80 Ω

Zener Diodes Question 15 Detailed Solution

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As R decreases current through it will increase.

Current supplied by 10V source is I=(10-6) / 50

I=80 mA
The maximum current through R is 80 - 5 = 75 mA

So Minimum \(R = \frac{V}{{{I_L}}} = \frac{6}{{75}}k\Omega \)

R = 80 Ω 

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