Zener breakdown is caused when there is a high electric field across the junction. 39. There is a hysteresis effect; once avalanche breakdown has occurred, the material will continue to conduct even if the voltage across it drops below the breakdown … The connection of the Zener is not-destroy whereas the avalanche is destroyed. We also got to know about Zener breakdown and Avalanche breakdown and various terms related to it. 8. Avalanche Breakdown. A. B) 2 PN junction . This is the Multiple Choice Questions in Special-Purpose Diodes from the book Electronic Devices – Electron Flow Version and Conventional Current Version 8th Edition by Thomas L. Floyd. Here, there is no specific breakdown voltage for the diode, although there is a relationship between the current and the applied voltage in reverse bias. The depletion region of the Zener is thin whereas the avalanche is thick. A. varactor diode. The current through the diode is (A) 10 mA (B) 15 mA (C) 20 mA (D) 5 mA. This is also known as avalanche multiplication. MCQs on PN junction diode : 1. On the other hand, the phenomenon of Avalanche Breakdown occurs because of the collision of electrons that are moving at a very high speed. The depletion region is thin. So, this is all about an overview of Zener breakdown and Avalanche breakdown. Zener Breakdown occurs when the PN-junction diode is highly doped while Avalanche Breakdown occurs only when the PN junction diode is very lightly doped. Theoretically, Zener breakdown occurs at a lower voltage level then avalanche breakdown in a diode, especially doped for Zener breakdown. Depletion region. Definition. PN Junction Diode Multiple Choice Questions Answers; 11. Zener breakdown. PN junction failure below 5 V is caused primarily by. The Zener breakdown voltage will vary inversely with temperature but the Avalanche breakdown voltage will vary directly with temperature. The Zener and Avalanche breakdown both occur in diode under reverse bias. As the magnitude of the reverse bias voltage across the diode increases, the kinetic energy will also increase. Avalanche and Zener effects. How is the breakdown region set during the manufacturing of the diode? Avalanche breakdown is defined as the process of applying a high voltage which increases the number of free electrons in the semiconductors and insulating materials. Zener Diode Multiple Choice Questions Answers; 41. A semiconductor device especially fabricated to utilize the avalanche or zener breakdown region. The avalanche breakdown occurs because of the ionisation of electrons and hole pairs whereas the Zener breakdown occurs because of heavy doping. The operating voltage is also different in Zener and Avalanche breakdown. We came to know about the functions of these diodes. The solved questions answers in this Test: Breakdown Diodes quiz give you a good mix of easy questions and tough questions. When high reverse voltage is applied to the p-n junction diode, the free electrons (minority carriers) gains large amount of energy and accelerated to greater velocities. C) 3 PN junction. The Avalanche Breakdown and Zener Breakdown are two different mechanisms by which a PN junction breaks. WatElectronics.com | Contact Us | Privacy Policy. This is normally operated in the reverse-region and its application is mostly for voltage reference or regulation. Avalanche diodes (commonly encountered as high voltage Zener diodes) are constructed to break down at a uniform voltage and to avoid current crowding during breakdown. Avalanche breakdown is not reversible while Zener breakdown is reversible. When the Vz is greater than 8 volts in a Zener diode, avalanche breakdown occurs because there is an isolation of electrons and holes. B. At low carrier density, avalanche breakdown is the dominant mechanism driving high current at high reverse bias voltage. The conventional current in a PN junction diode flows: (a) From positive to negative (b) From negative to positive (c) In the direction opposite to the electron flow. The cut in voltage (or knee voltage) of a silicon diode is (a) 0.2V (b) 0.7V (c) 0.8 V (d) 1.0V Answer-B 3. 1. A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in the figure. D. Schottky barrier diode When the reverse bias voltage starts to increase, the diode intentionally starts an avalanche effect at a … Zener breakdown occurs when the high electric field is created across the junction. 407. A: The Zener diode allows current to flow not only from its anode to its cathode, but then also in the reverse direction when the Zener (breakdown) voltage is reached (Figure 6). The current in a Zener diode is controlled by, D.Has a constant current passing through it, 45. This feature of avalanche diode provides better surge protection as compared to a Zener diode. Can't read the image? The main difference lies in the operation of the two diodes. Answer. 400 V If the applied reverse voltage across the diode is more than Zener voltage, the diode provides a conductive path to the current through it hence, there is no chance of further avalanche breakdown in it. This type of junction breakdown is called avalanche breakdown. In Zener breakdown, the increase in reverse voltage causes the expansion of the depletion layer. Both P and N are lightly doped. Difference Between Von Neumann and Harvard Architecture? Contact us: info@mechanicaltutorial.com, Has a constant current passing through it. Both P and N are heavily doped. B. Zener breakdown. Negative resistance characteristic exists; Forward voltage rating is high; Sharp breakdown occurs at a low reverse voltage; All of the above; Answer: (c) Sharp breakdown occurs at a low reverse voltage. The avalanche breakdown occurs in both normal diodes and zener diodes at high reverse voltage. A. d) Both (a) and (c) above Answer-A 2. B. zener diode. 7. Zener diode is a special kind of diode that allows current to flow in the forward direction in the same manner as an ideal diode, but also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage of Zener diode, Zener knee voltage or Zener voltage. MCQs on Zener Diode. What is the Difference Between Electronic Devices And Integrated Circuit? Lowest; Moderate; High; Low; Answer:(c) High. The diode may use either zener breakdown or avalanche breakdown. 41. Commonly, Zener diodes are available with breakdown voltage between 1.8 to 200 Volts. Click here to refresh, © 2015 - 2020 MechanicalTutorial.com This Content is copyrighted By MechanicalTutorial.com |All Rights Reserved. Avalanche Breakdown occurs due to the collision of accelerated charge carriers with the adjacent atoms and due to carrier multiplication. Another difference lies in the nature of doping. Difference Between Avalanche & Zener Breakdown One of the major difference between the Avalanche and the Zener breakdown is that the Avalanche breakdown occurs because of the collision of the electrons, whereas the Zener breakdown occurs because of the high electric field.The other differences between them are explained below in the comparison chart. Multiple Choice Questions and Answers on Semiconductor Diode In addition to reading the questions and answers on my site, I would suggest you to check the following, on amazon, as well: Question Bank in Electronics & Communication Engineering by Prem R Chadha In a Zener diode with high breakdown voltage, 42. The associated phenomenon is called Avalanche Breakdown (shown in red color in the figure) and the corresponding voltage is Avalanche Breakdown Voltage (V BR), which is a central phenomenon to the working principle of avalanche diodes. D) 4 PN junction. This will cause more and more electrons to collide with one another resulting in the generation of current. C. Either P or N is lightly doped. Zener breakdown occurs when the operating voltage is less than 5V while the Avalanche breakdown occurs when the operating voltage is greater than 5V. If you are looking for a reviewer in Electronics Engineering this will definitely help. This contains 10 Multiple Choice Questions for Electrical Engineering (EE) Test: Breakdown Diodes (mcq) to study with solutions a complete question bank. C. Either of … When PN junction diode is forward bias, forward current is dominated by The diffusion current The displacement current The drift current The drift or diffusion current Answer – (1) 3. The diode using avalanche breakdown uses medium doping and is characterized by breakdown voltage exceeding 6 volts. 400/√2 V. B. The avalanche breakdown is an occurrence of raising the flow of electric current or electrons in insulating material or semiconductor by giving the high voltage. Diode using zener breakdown uses heavy doping of the order of 1 impurity atom per 10 5 silicon atoms and is 10 6 volt/cm. Another special type of diode called the Avalanche diode is used for circuit protection. C. shockley diode. It occurs in the Zener diodes having Vz between 5 to 8 volts or less than 5V. The depletion region is thick. The crucial difference between the Zener and Avalanche breakdown is the operating mechanism. What is the Difference Between GSM and CDMA. The device is named after Clarence Zener who discovered this electrical property. In Zener diode, the breakdown is due to Zener, has doping, Enter the code above here : 40. C) reverse bias exceeds a certain value. On the other hand, Avalanche Breakdown occurs in the device due to the collision of electrons moving at high speed. Q6: In a Zener diode. Another major difference between the Avalanche and Zener breakdown is the movement of the conduction band and valance band. The efficiency of Avalanche breakdown can be expressed in terms of multiplication factor, M given by When forward-biased, the Zener diode behaves like a normal silicon diode with PN junction, allowing a current to pass from the anode to the cathode. Avalanche Breakdown. Zener Breakdown occurs in heavily doped diodes while Avalanche breakdown takes place in a lightly doped diode. Avalanche diodes are specially designed for avalanche breakdown and they experience a voltage drop because of the breakdown conditions. diodes marketed as "zener diodes" with breakdown above 6V), there can be a very small range of current where hysteresis is possible, and one can build a relaxation oscillator. This causes the stationary electrons to move towards the conduction band. Unlike Zener diodes, the avalanche diodes maintain a voltage that is higher than the breakdown voltage. NEET Physics Zener Diode Multiple Choice Questions make you feel confident in answering the question in the exam & increases your scores to high. Avalanche breakdown. Q7: A Zener diode, having breakdown voltage equal to 15 V, is used in … In Zener diode, the Zener breakdown takes place, 43. Can you mention a few, What is a Ballistic Galvanometer : Construction & Its Working, Arduino Technology Architecture and Its Advantages, Embedded Systems Role in Automobiles with Applications, Traffic Light Control System using Microcontroller, Light Sensor Circuit Diagram with Working Operation, What is 555 Timer IC – Working with Operating Modes, What is RISC and CISC Architecture and their Differences. As far as I know, real avalanche diodes don't have oscillation of this type. The temperature coefficient of Avalanche and Zener breakdown is also different. Zener Breakdown has a negative temperature coefficient while Avalanche Breakdown has a positive temperature … Zener diode has… A) 1 PN junction. Electric connection. In a Zener diode with a high breakdown voltage has (a) Lightly doped P and N (b) P or N is lightly doped (c) Heavily doped P and N (d) None of these. If the a.c. input to a half-wave rectifier is an r.m.s value of 400/√2 volts, then diode PIV rating is_____? D. None of the above NEET Physics PN junction diode Multiple Choice Questions make you feel confident in answering the question in the . D) none of the above The voltage at which the breakdown occurs is called the breakdown voltage. However, Zener Breakdown occurs due to the breaking of covalent bonds by the strong electric field across the junction. B) forward current exceeds a certain value. This high current can cause the breakdown of the diode. Avalanche breakdown in a crystal diode occurs when. The construction of Avalanche diode is similar to the Zener Diode and both Zener and avalanche breakdown is present in these diodes.It is used in avalanche breakdown condition so they have small but significant voltage drop under breakdown condition but the Zener diode always maintain the voltage higher than the breakdown.This feature of diode provide better surge protection than a Zener diode. A Varactor Diode performs as A variable resistor A variable capacitor A switching device none of these Answer – (2) 2. 1. These diodes can indefinitely sustain a moderate level of current during breakdown. A) the potential barrier is reduced to zero. In the case of Avalanche breakdown, the valence band will be pushed in the direction of the conduction band. Answer: (C) Sharp breakdown occurs at a low reverse voltage. Aha, to answer my own question I see that for some avalanche diodes (i.e. A. Avalanche breakdown. Answer: (D) 5 mA. In a Zener diode with high breakdown voltage. 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( c ) above Answer-A 2 info @ MechanicalTutorial.com, has a constant current passing through it 45... This is normally operated in the Zener and avalanche breakdown occurs at a lower voltage then!