Zener Diode Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. Which of the following can be used in series with a Zener diode so that the combination has almost zero temperature coefficient?

1. MOSFET
2. Resistor
3. Transistor
4. Diode

Ans. The correct answer is d. Diode

Explanation: When a Zener diode with a temperature coefficient of approximately -2mV is connected in series with a forward diode with a temperature coefficient of about +2mV, the combination may be utilized to generate an extremely low (near to zero) temperature coefficient.

Ques. Zener diodes are also known as

1. Breakdown diode
2. Forward bias diode
3. Voltage regulators
4. None of the above

Ans. The correct answer is a. Breakdown diode

Explanation: Although zener diodes are used as voltage regulators, they are not referred to as voltage regulators. They are known as breakdown diodes because they function in the breakdown region.

Ques. Zener diodes can be effectively used in voltage regulators. However, they are these days being replaced by more efficient

1. MOSFET
2. Operational Amplifier
3. Integrated Circuits
4. None of the above

Ans. The correct answer is c. Integrated Circuits

Explanation: Integrated Circuits have been widely used by industry to provide better voltage regulator alternatives for conventional zener diodes.

Ques. Operation of the Zener diode depends on the heavy doping of its

1. N-junction only
2. P-junction only
3. P-N junction
4. None of the above

Ans. The correct answer is c. P-N junction

Explanation: The operation of a Zener diode depends on the heavy doping of its P-N junction. This is because the heavy doping creates a narrow depletion region at the junction, which is necessary for Zener breakdown to occur.

Ques. Which of the following is true about the resistance of a Zener diode?

1. It has dynamic resistance
2. It has an incremental resistance
3. The value of the resistance is the inverse of the slope of the i-v characteristics of the Zener diode
4. All of the above

Ans. The correct answer is d. All of the above

Explanation: The resistance of a Zener diode depends on the operating point. In the normal operating region (forward bias), the resistance is low. However, in the breakdown region, the resistance becomes high and is referred to as dynamic resistance or incremental resistance. The value of the dynamic resistance is inversely proportional to the slope of the I-V characteristics of the Zener diode.

Ques. In the Zener diode, for currents greater than the knee current, the V-I curve is almost

1. Almost a straight line parallel to the x-axis
2. Equally inclined to both axes with a negative slope
3. Almost a straight line parallel to the y-axis
4. Equally inclined to both axes with a positive slope

Ans. The correct answer is a. Almost a straight line parallel to the x-axis

Explanation: In the Zener diode, for currents greater than the knee current, the V-I curve is almost a straight line parallel to the x-axis.

Ques. The Zener diode is used as the surge suppressor.

1. True
2. False

Ans. The correct answer is a. True

Explanation: Zener diodes suppress transients by clamping potentially damaging currents away from the protected load.

Ques. Diodes are used in logical gates.

1. True
2. False

Ans. The correct answer is a. True

Explanation: Diodes are used in clipping circuits, clamping circuits, logic gates, and rectifiers.

Ques. The opposition offered to the flow of electricity through the Zener diode in the operating region is known as

1. Zener Capacitance
2. Zener breakdown
3. Zener Resistance
4. Zener Current

Ans. The correct answer is c. Zener Resistance

Explanation: Zener resistance is the opposition offered to the flow of electricity through the Zener diode in the operating region.

Ques. Zener current is measured in

1. Luminous intensity
2. Kelvin
3. Watts
4. Ampere

Ans. The correct answer is d. Ampere

Explanation: Zener current is the current that flows through a Zener diode when it is operated in the breakdown region. It is measured in amperes (A).

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Short Answers Questions [2 Marks Questions]

Ques. What is the Zener diode?

Ans. A Zener diode is a type of diode that allows current to flow "backward" when a particular reverse voltage, also known as the Zener voltage, is reached.

Ques. What is Zener voltage?

Ans. The voltage at which a Zener diode begins to conduct in the opposite direction is referred to as the Zener voltage. Zener diodes have a unique feature that makes them useful for voltage regulation applications.

Ques. Does Zener Diode work in forward-biased mode?

Ans. A Zener diode does not operate in forward-biased mode. For its intended applications, it is designed to operate in reverse bias.

Ques. Zener diodes are developed to conduct in the reverse direction when a specified voltage is reached. What is this voltage known as?

Ans. This type of voltage is referred to as the Zener voltage. The reverse breakdown requirement is satisfied by the Zener voltage, allowing the diode to conduct in the reverse direction.

Ques. What is the formula to calculate the Zener resistance?

Ans. Zener resistance can be calculated by the formula

Zener Resistance (R_Z) = Zener voltage (V_Z)/Zener current (I_Z)

Ques. What are the types of breakdowns for a Zener Diode?

Ans. The following are the different types of breakdowns in a Zener diode

• Avalanche Breakdown
• Zener Breakdown

Ques. What is the difference between a Zener diode and a normal diode?

Ans. The main difference between a Zener diode and a normal diode is their current conduction. A normal diode only allows current to flow in one direction, but a Zener diode enables current to flow in both directions.

Ques. What is a diode?

Ans. A diode is a two-terminal electrical component that typically conducts current in one direction. It has low resistance in one direction and strong resistance in the other.

Ques. What is a PN junction?

Ans. A p-n junction is an interface or border between two types of semiconductor materials, p-type and n-type, within a single semiconductor crystal. In the outer shells of the electrically neutral atoms on the "p" side, there are more holes than electrons. On the "n" side, there are more electrons than holes.

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Long Answers Questions [3 Marks Questions]

Ques. How is the Zener diode used as a voltage regulator?

Ans. Shunt Voltage Regulators, such as Zener Diodes, are commonly used to regulate voltage across small loads. 

• Zener diodes have a sharp reverse breakdown voltage and a stable breakdown voltage over a wide range of currents. 
• As a result, we will connect the zener diode in parallel to the load, causing the applied voltage to reverse bias it. 
• The voltage across the load will be constant if the reverse bias voltage across the Zener diode exceeds the knee voltage.

Ques. What are the reverse characteristics of the Zener diode?

Ans. When a reverse voltage is applied to a zener diode, a small amount of current will still flow across the diode. 

• This is due to thermally generated minority carriers. 
• As the reverse voltage increases, there will be a point where the current suddenly increases sharply. 
• This is called the breakdown voltage, or Zener voltage, and it is the point at which the diode breaks down and starts to conduct current heavily.

Ques. What is Avalanche Breakdown in Zener Diode?

Ans. Avalanche breakdown can happen in both regular diodes and Zener diodes when they are subjected to a high reverse voltage. 

• When a high reverse voltage is applied to the PN junction, the electrons gain enough energy to move very quickly. 
• These fast-moving electrons bump into other atoms, knocking loose more electrons. 
• This chain reaction creates a lot of free electrons, which causes a sudden increase in electric current through the diode. 
• In a regular diode, this sudden surge in current can damage the diode permanently. 
• However, Zener diodes are designed to handle avalanche breakdowns and can withstand the sudden spike in current. 
• Avalanche breakdown usually happens in Zener diodes with a Zener voltage (Vz) greater than 6 volts.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the applications of the Zener diode?

Ans. The following are the applications of the Zener diode

• As a voltage regulator: When the load voltage equals the breakdown voltage, the series resistors limit the current flowing through the diode when there is an excess of voltage when the diode is conducting. While doing so, the diode produces noise, which may be reduced by connecting a large decoupling capacitor across the diode.

• Protects from overvoltage: When the input voltage rises to the Zener breakdown voltage, the current flowing through the diode causes a voltage drop across the resistor. This causes a short circuit to ground.

• Used in clipping circuits: Clipper circuits are used to prevent the output signal from exceeding a certain value while leaving the input signal unchanged. Zener diode applications include changing and shaping AC waveform clipping circuits. Clipping circuits shape or protect the waveform by limiting one section of the AC waveform. These circuits are commonly used to reduce interference in TV and FM transmitters.

• Used to shift voltage: The primary application of a Zener diode is to transfer a signal from one voltage to another. It can maintain a constant output voltage in the breakdown area. Because of this voltage-changing capability, the zener diode is an excellent component of the operation.

Ques. What are the advantages of Zener diode?

Ans. The advantages of Zener diodes are

• The Zener diode is less costly than other types of diodes.
• This diode can be used to regulate and stabilize the voltage in a circuit.
• These diodes have a high-performance standard
• Control the current flow
• Compatibility and accessibility
• It can be used in a smaller circuit that would not work with any larger form of the current regulation.
• Because of their cheaper cost and higher control, they are compatible with the majority of systems.

Ques. What is the difference between Zener Breakdown and Avalanche Breakdown?

Ans. The following are the differences between Zener Breakdown and Avalanche Breakdown

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