Electronic Devices and Circuits Questions and Answers – Zener Diode

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Zener Diode”.

1. Zener diodes are also known as
a) Voltage regulators
b) Forward bias diode
c) Breakdown diode
d) None of the mentioned
View Answer

Answer: c
Explanation: Zener diodes are used as voltage regulators but they aren’t called voltage regulators. They are called breakdown diodes since they operate in breakdown region.

2. Which of the following is true about the resistance of a Zener diode?
a) It has an incremental resistance
b) It has dynamic resistance
c) The value of the resistance is the inverse of the slope of the i-v characteristics of the Zener diode
d) All of the mentioned
View Answer

Answer: d
Explanation: All of the statements are true for the resistance of the zener diode.

3. Which of the following is true about the temperature coefficient or TC of the Zener diode?
a) For Zener voltage less than 5V, TC is negative
b) For Zener voltage around 5V, TC can be made zero
c) For higher values of Zener voltage, TC is positive
d) All of the mentioned
View Answer

Answer: d
Explanation: All of the mentioned are true for the TC of a zener diode.
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4. Which of the following can be used in series with a Zener diode so that combination has almost zero temperature coefficient?
a) Diode
b) Resistor
c) Transistor
d) MOSFET
View Answer

Answer: a
Explanation: If a Zener diode of TC of about -2mV is connected with a forward diode (which has a TC of about +2mV) in series, the combination can be used to obtain a very low (close to zero) TC.

5. In Zener diode, for currents greater than the knee current, the v-i curve is almost
a) Almost a straight line parallel to y-axis
b) Almost a straight line parallel to x-axis
c) Equally inclined to both the axes with a positive slope
d) Equally inclined to both the axes with a negative slope
View Answer

Answer: b
Explanation: Note that the curve is v-I curve and not an i-v curve.

6. Zener diodes can be effectively used in voltage regulator. However, they are these days being replaced by more efficient
a) Operational Amplifier
b) MOSFET
c) Integrated Circuits
d) None of the mentioned
View Answer

Answer: c
Explanation: ICs have been widely adapted by the industries over conventional zener diodes as their better replacements for a voltage regulators.

7. A 9.1-V zener diode exhibits its nominal voltage at a test current of 28 mA. At this current the incremental resistance is specified as 5 Ω. Find VZ0 of the Zener model.
a) 8.96V
b) 9.03V
c) 9.17V
d) 9.24V
View Answer

Answer: b
Explanation: VZ = VZo + MZ IZT
9.1 = VZo + 5 * 28 * 10-3
VZo = 8.96v
VZ = VZo + 5IZ = 8.96 * 5IZ.
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8. A shunt regulator utilizing a zener diode with an incremental resistance of 5 Ω is fed through an 82-Ω resistor. If the raw supply changes by 1.0 V, what is the corresponding change in the regulated output voltage?
a) 72.7 mV
b) 73.7 mV
c) 74.7 mV
d) 75.7 mV
View Answer

Answer: c
Explanation: The change in regulated output voltage is 74.7 mV If the raw supply changes by 1.0 V

9. A designer requires a shunt regulator of approximately 20 V. Two kinds of Zener diodes are available: 6.8-V devices with rz of 10 Ω and 5.1-V devices with rz of 30 Ω. For the two major choices possible, find the load regulation. In this calculation neglect the effect of the regulator resistance R.
a) -30mV/mA and 120mV/mA respectively
b) 30mV/mA and 60mV/mA respectively
c) -60mV/mA and +60mV/mA respectively
d) -30mV/mA and -120mV/mA respectively
View Answer

Answer: d
Explanation: Three 6.8v zeners provide 3*6.8 = 20.4v with 3 * 10 =30Ω Resistance, neglecting R, we have
load Regulation = -30mV/mA.
For 5.1 Zeners we need 4 diodes to provide 20.4v with 4 * 30 =120Ω Resistance.
load Regulation = -120mV/mA .
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10. Partial specifications of a Zener diode is provided. VZ = 10.0 V, VZK = 9.6 V, and IZT = 50 mA. Assuming that the power rating of a breakdown diode is established at about twice the specified Zener current (IZT), what is the power rating of each of the diodes described above?
a) 1.04 W
b) 0.104 W
c) 10.4 mW
d) 1.04 mW
View Answer

Answer: a
Explanation: Power rating of diodes is 1.04 W if Zener diode is provided VZ = 10.0 & VZK = 9.6 V

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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