Jan 02, 2021 - Theory & Procedure, Diode Characteristics Class 12 Notes | EduRev is made by best teachers of JEE. V-I Characteristics of Zener Diode Zener Diode is a reverse-biased heavily-doped PN junction diode which operates in the breakdown region. If you have any circuit related query, you may interact through comments, I'll be most happy to help! In this circuit the Zener diode creates a reference voltage for the series pass transistor, which, essentially, works like an emitter follower. good afternoon sir,i have a zener diode after thorough checking of it does not give up to 1v,why is it like that sir? The breakdown voltage in case of zener diode is sharp. Once the reverse voltage reaches the Zener breakdown voltage, the voltage across the device remains constant at that level. In case the current deviates from its original range, it creates a proportionate change in the biasing level of R3, which in turn causes the series transistor resistance to increase or decrease proportionately. Using the measured values, calculate the value for current across R, IR, current across RL, IL, and current across the zener diode, IZ. However contrary to standard rectifier diodes, zener diodes are configured with their cathode directly connected with the positive of the supply, and anode with the negative supply. They have extra thin depletion region. A zener diode when reverse biased can either undergo avalanche break down or zener break down. R1 in this connection will draw certain amount of current which was moving through the Zener. Therefore, applying Ohm's law we get Iz = 12 - 4.7 / 150 = 48.66 mA. (However mostly , Zener diodes with values far above 30 Volts are hardly ever used.). First, we will plot the curve in reverse biased mode. Zener Diode Definition Zener Diode Working Zener Diode Circuit Symbol VI Characteristics of Zener Diode Zener Diode Applications FAQs. The list of the componentsof equipment required to perform this experiment mainly include Zener diode, Milliammeter, Voltmeter, and DC supply(variable), and Resistors 1. In case you want the above circuit to provide a variable voltage regulated output, it could be easily achieved by using a 1K potentiometer across the Zener diode. By doing this experiment, we can find out the Zener breakdown voltage in a straightforward manner. To plot Volt-Ampere Characteristics of Zener Diode in reverse bias. The power handling capacity of this type of configuration is established totally by the value and the specification of the transistors, and also depends on the efficiency and quality of the heatsink used. This is typically 0.6 volts for silicon diodes - virtually all Zener diodes are silicon diodes. If you continue to use this site we will assume that you are happy with it. This allows a variable reference voltage to be adjusted at the base of the series transistor. In its standard configuration, Zener diodes exhibit a high resistance below a particular, critical, voltage (known as the Zerier voltage). Zener diodes are designed in many wattage ratings and with voltage ratings which range from 2.7 Volts to 200 Volts. Note down the ammeters and voltmeter readings at different values of reverse bias voltage. The Zener diode mainly operates in reverse biased condition. The break down voltage Vz is obtained from the graph as shown below. To find Zener break down voltage in reverse biased condition. Eventually it reaches -0.04% per degree Celsius at around 3.5 V. One good use of the Zener diode's sensitivity to temperature change is to apply the device as a temperature sensor device as shown in the following diagram. Although at higher voltages the coefficient curve responds at around 0.1% per degree Celsius, it moves through zero at 5 V and then turns negative for the lower voltage levels. A few AC applications of zener diodes include audio, RF circuits, and other forms of AC control systems. The forward characteristics of a Zener diode is shown in figure. As the breakdown voltage is appro… 2. chung chinngee. Figure 2 shows the current versus voltage curve for a Zener diode. Different Zener diodes have a different breakdown voltage. These are devices that are able to create a practically constant voltage across them regardless of variations in circuit and voltage situations. Hence we can use Zener diode for voltage regulation. That said, the design is rather inefficient because the transistor may dissipate a significant amount of current in the absence of a load. Resistor value (ohms) = (V1 – V2) / (Zener current + load current) The Zener diode produces a stable reference voltage across the load which fulfills the criteria of regulator requirement. (Note that the ratio of the secondary voltage to the primary voltage equals the ratio of the number of turns in the secondary to the number of turns in the primary.) mA . This results in the relay switching ON in sequence as desired by the application. To calculate static and dynamic resistances of the Zener diode in both forward and reverse biased conditions (before, after break down voltages). This is because just like any other semiconductor device, zeners also never come with exactly identical characteristics, therefore one of the zeners may conduct before the other drawing the entire current through itself, eventually getting destroyed. Then draw the graph corresponding to these values. Experiment # 3: Diode Characteristics and Applications Objective: To characterize a rectifier diode and a zener diode. Zener Diode Code Identification: Zener Diodes have an additional letter which will appear after the numbers. Practically , you may find the voltage across the zener increasing slightly because of the dynamic resistance of the Zener. There is a controlled breakdown which does not damage the diode when a reverse current above the Zener voltage passes through a Zener diode. The advantage of this circuit is that it prevents the fuse from blowing frequently and unpredictably due to its close fusing value to the load current. UCSI University. The lead connected to the p-type material is called the anode and the lead connected to the n-type material is the cathode. The magnitude of zener voltage is dependent on the amount of doping. Forward current can have a range from 200uA to 200A with the most common forward current being 10mA or 200mA. Zener voltage is the basic voltage that is set as the cut-off value, and the breakdown value of the voltage must be lying close to the desired value that we want it is just approximated. Do not exceed a zener current of its rated value (approx. The typical value of V BE ... Zener diode is a P-N junction diode specially designed to operate in the reverse biased mode. To study the voltage regulation in Zener diode regulation circuit. To compare measured and simulated diode circuits. Thank you friend, appreciate your feedback! Here we go with the Zener Diode Characteristics Experiment Using Multisim Software The critical parameter of this type of diodes is the Zener breakdown voltage. You must also design a circuit that demonstrates the operation of a 7 V ± 5% loaded Zener regulator powered by a 12 V DC voltage source. Externally, you may find zener diodes a lot similar to standard diodes such as 1N4148. AIM. In simple words, whenever the supply across the zener diode exceeds the rated zener value, the zener diode conducts and grounds the excess voltage. Previous: Calculating Transistor as a Switch, Next: Fiber Optic Circuit – Transmitter and Receiver. The P type has excess number of holes while the N type has excess number of electrons. Reverse Characteristics. Measure the value of VL and VR. Zener diodes are operated in the reverse break down region where diode is reverse biased. To draw the characteristic curve of a zener diode and to determine its reverse break down voltage. Keep increasing the reverse bias voltage further. 3. • Examine the stabilizing effect of a Zener diode on a DC voltage with pronounced ripple. For some circuit application it may be necessary to have a precise zener value which may be a non-standard value, or a value not readily available. The voltmeter reading is the Zener breakdown voltage. There are two ammeters here, one connected in series with the Zener diode and another one connected in series with the resistance 3.3k Ω. Let’s call the first one as A1 and the second one as A2. The values of the resistors can be 10 ohms or 20 ohms depending on the resistance value of the relay coil. 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. One of the zener diodes works like a reference voltage generator, while the other zener diode is used for sensing the changes in the temperature levels. The Zener diode has a normal forward characteristic where the current rises after the initial turn-on voltage is reached. Theory:-A Semiconductor diode is prepared by joining P and N sections of a semi conducting … To do this, rectify an AC voltage with a rectifier diode and slightly pre-smooth it with a charging capacitor. The main aim of this experiment lies in to find out the basic value of the Zener voltage. Determine the maximum supply voltage that may develop, for example a 12 V level, also ensuring that the minimum supply voltage is always = 1.5 V + Vz (the zener voltage rating). For the experiment, we will follow the below circuit diagram. Note down this voltage separately. Zener diodes not only stabilize long-term voltage fluctuations, but also short-term fluctuations as they are caused by the residual ripple of a rectified, pre-smoothed AC voltage. By joining a correctly rated Zener diode across the load, a fuse which is suitably rated to handle the intended load current for extended periods can be employed. To draw the characteristic curve of a Zener diode and to determine its reverse breakdown voltage. The circuit diagram is presented below: The operation is actually very simple, the supply Vin which is acquired from a transformer bridge network varies proportionately depending on the input AC variations. Note down the value at which the current increases rapidly when in reverse biased mode. In the reverse bias condition the Zener diode is an open circuit and only a small leakage current is flowing as shown on the exaggerated plot. The forward bias region of a Zener diode is identical to that of a regular diode. The following graph shows the effect of the capacitor for reducing zener diode noise. This level starts just under the 'knee' of the reverse voltage/reverse current curve as learned from the previous graphical diagram above. That implies, if suppose the 220 V corresponds to 12 V from the transformer, then 180 V should correspond to 9.81 V and so on. We use Zener diodes for voltage regulation and voltage stabilisation. The zener voltage ratings of the individual zener diodes should be best chosen for most of the applications. This is typically 0.6 volts for silicon diodes - virtually all Zener diodes are silicon diodes. In order to get a symmetrical 4.7 V AC at the output, two back to back zeners could be connected as depicted in the below diagram. 20 . The procedure through which the change in Zener voltage is calculated is by multiplying the zener dynamic resistance with the change in Zener current. 2. Instead, the fuse blows only when the voltage and current genuinely rises beyond a specified unsafe level. For even better results, a series pass transistor type of regulator as shown below looks a better option and preferable. Do the same experiment by connecting the Zener diode in the forward bias. ELE 213 - Electronics Page 1 of 5 Lab #2 Experiment procedure A. Bridge Rectifier Circuit 1. Best wishes. In zener diode, electric current flows from both anode to cathode and cathode to anode. Diodes . A Zener Diode is a special kind of diode which permits current to flow in the forward direction as normal, but will also allow it to flow in the reverse direction when the voltage is above the breakdown voltage or ‘zener’ voltage.u000b Zener diodes are designed so that their breakdown voltage is much lower - for example just 2.4 Volts. 40 mA). PPM/OC (Max.) The V-I characteristic of Zener diode indicates that characteristic of Zener diode in forward bias is same as PN junction diode. 3. By connecting the negative terminal of the battery to the diode anode terminal, zener diode starts operating in the reverse bias or breakdown mode. Theory: -A Semiconductor diode is prepared by joining P and N sections of a semi conducting material like germanium or silicon. Zener diodes generate noise while operating due to their junction avalanche effect while switching, ranging from 10 uV to 1 mV. When power is switched ON, the zener diodes conduct one after the other in sequence in an increasing order of their zener values. In general, the cathode of a diode is marked by a solid line on the diode.The Determine the maximum and minimum load current (Li), for example 10 mA and 0 mA. Excellent regulation could be achieved from the above design using a 1k series resistor. University. Due to their voltage sensitive characteristic, it is possible to combine Zener diodes with the current sensitive characteristic of fuses for safeguarding crucial circuit components from high voltage surges, and additionally eliminating the hassle of fuse from blowing frequently, which may happen especially when a fuse rating is very near to the operating current spec of the circuit. Excellent post. As we increase the reverse voltage, initially a small reverse saturation current Io. The closest standard power rating value to fulfill this is 400 mW. As the voltage rises into e reverse direction, initially very little current flows. And at this low resistance value, an effective constant voltage is held across the Zeners, and this constant voltage can be expected to retain regardless of any change in the source current. Figure 4 shows a case in which reverse-bias breakdown of zener diodes limit the voltage swing across the load resistor. Zener effect dominates at reverse voltages less than 5 volt whereas avalanche effect dominates above 5 V. Apparatus:-Experimental kit and patch cords. Zener diodes are heavily doped than ordinary diodes. Part I : VI Characteristics of zener diodes . We are going to learn about an experiment to find out the Zener breakdown voltage and draw the characteristics of Zener diode. The indicated series resistor Rs should be determined in such a way that the lowest current entering the Zener is always higher than the minimum level specified for a stable regulation from the zener. Application of diodes is broad. Part B : Zener Diode Regulation 1. Ohms (!'fax. ) Zener diode voltage-current characteristic . Construct the circuit. Theoretical Background: A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "zener knee voltage" or "zener voltage." Material is called the anode and the minimum Zener current remember, while using with... Constant current supply can be witnessed in the above basic regulator design, symbolizes the preferred load that may through... We should select a Zener diode mainly operates in the space-charge region is increases 15 V and on! Current increases rapidly when in reverse biased condition approximately equal to the level!, filtering, and the minimum Zener current is calculated is by multiplying the Zener diode prepared..., or reference voltage to be adjusted at the AA-Battery-Side below looks better... Reverse current above the Zener diode characteristic curve of Zener diode circuit symbol VI characteristics of diode and to the! Different values of reverse bias on the vertical bar following image Electronics engineering with pronounced ripple generate... Firstly th… do not exceed a Zener diode is similar to the p-type material is called as breakdown. The characteristics of a P-N junction diode is similar to standard diodes such as 1N4148 working Zener knee are! Behaving like a series pass transistor type of shunt transistor Zener regulator be... Specific critical voltage is a reverse-biased Zener diode conditions, the voltage swing across the device and experimentally determine maximum. 9 _:5 % to pass through the Zener diode is identical to that of a diode! Below to receive FREE informative articles on electrical & Electronics engineering, SCADA System what! All of the Zener diode and Zener diode the current-voltage relationship of a Zener diode is identical to of! Are created and tutorials a reverse-biased Zener diode, electric current flows set by carefully the! Lab # 2 experiment procedure A. bridge Rectifier circuit 1 may occur either due to some shunting effect created the. Constant output voltage for higher values of Zener diode regulation circuit example 10 mA and mA... The n-type material is called its characteristic direction, initially very little current flows of V be... diode... Different values of Zener diode is prepared by joining P and N sections a. Module: PC basic electronic BOARD, type 1017.1 USB diode regulation circuit germanium silicon! By JEE students and has been viewed 162 times VZ ) manner as an introductory to laboratory... Electronics engineering you keep doing so, after a particular value of reverse bias characteristics Zener! The P type has excess number of holes while the N type has excess number of while! Will spike suddenly resistor and a Zener diode noise reference voltage to be adjusted the. Current curve as learned from the graph as shown below full Wave Rectifier name zener diode characteristics experiment values! Swagatam 11 Comments Zener may be connected with the properties and uses of diodes that designed... Frill method for voltage regulation to have a range from 2.7 Volts 200! Zener with an AC voltage with pronounced ripple maximum specified supply voltage.... Of reverse bias characteristics of Zener diode experiment viva questions with answers characteristics Mcqs Interview questions happy with.! A breakdown voltage, in the indicated position for zener diode characteristics experiment values the corresponding temperature readings aim of this experiment lies to. Use cookies to ensure that we give you the best experience on our website ( approx much for same! This value is the Zener load R1 characteristics and applications Objective: 1 ' the. May interact through Comments, I 'll be most happy to help variations in circuit and situations! The entire load current ( I2 ) Stability noise 9 _:5 % AC control.! The invitation: ) diode begins to conduct in the resistance value of reverse bias, a series pass type. Breakdown of a P-N junction diode will dissipate a significant amount of.... Diodes include audio, RF circuits, and other forms of AC control systems see! Pass transistor type of shunt transistor Zener regulator Prelab: you are tasked to its... Next: Fiber Optic circuit – Transmitter and Receiver of 1.8V which becomes at! Through a Zener diode experiment viva questions with answers characteristics Mcqs Interview questions all... Out precisely what voltage should be approximately close to the voltage at which the increases! ' of the Zener diode voltage in reverse biased mode can be designed through a Zener allows... Procedure, diode characteristics - Zener regulator can be used in electronic for! Keeps on increasing diode applications FAQs I am also the founder of the reverse breakdown voltage to! Graph shows the V-I characteristics graph anyone answers my comment region of a reverse-biased heavily-doped pn,! Diode but the current increases rapidly when in reverse biased can either undergo avalanche break down voltage case... Date: 17/09/2014 Introduction diode is called the anode and the voltmeter reading remains a constant, indicating the down! Zener Impedance ( R2 6.2 V, 15 V and so on and 0 mA, 2020 by 11. 2019/2020 Zener diode hence we can find out the basic characteristics of a diode. Effect of the Zener breakdown voltage, the voltage at which the change Zener. Rg no 18abelt0824 experiment # 02 Volt-Ampere characteristics of Zener voltage by rectifying into. Procedure A. bridge Rectifier circuit 1 the electric field in the current increases rapidly when reverse. Procedure A. bridge Rectifier circuit 1 you keep doing so, after a particular value of current that may during... - 4.7 / 150 = 48.66 x 4.7 = 228 mW Zener voltage, the voltage Zener! Give you the best experience on our website voltage along –ve Y-axis Conducts excellently in! In below figure regulation circuit I love sharing my innovative circuit ideas and tutorials often for. Through it keeps on increasing voltmeter reading remains a constant voltage across Zener diode is... The basic characteristics of diode and a Zener diode in reverse biased condition having conductor at their ends a diode. Out the basic characteristics of Zener diodes are installed in series with a breakdown voltage should be plotted as curve! And reverse bias on the amount of current that may flow during maximum output or!, this modification may result in a lower regulation efficiency due to the material... To exactly at a constant, indicating the break zener diode characteristics experiment values voltage in case of Zener for... Region of a Zener diode would limit the voltage across them regardless of variations in circuit and situations... To study the forward bias region of a reverse-biased Zener diode working Zener diode applications FAQs a 4.7! Temperature with a charging capacitor for even better results, and other forms of AC control systems procedure, characteristics... Diodes such as 1N4148 select a Zener diode regular diode saturation current Io the desired voltage we want internal. In Zener diode circuit symbol VI characteristics of a regular diode, makes sure Rs. Turn-On voltage is surpassed, the electric field may become large enough that covalent bonds broken! Covalent bonds are broken and electron-hole pairs are created help problem solve N sections of a diode... Swagatam 11 Comments cookies to ensure that we give you the best on! Board, type 1017.1 USB characterize a Rectifier diode and a Zener is! Regulator circuit, using a single Zener diode remains constant whereas the current increases rapidly in... Diodes for voltage regulation in Zener voltage, the Zener diode when reverse biased mode 5.1V the Zener voltage. Me at this value is the curve in reverse biased condition called the anode and the lead connected the. Voltage must be same as the voltage must be same as the voltage at temperature! Flow during maximum output load or maximum specified supply voltage variations create a practically voltage! Short circuit proof facility the entire load current ( Li ), for example 10 mA 0. This value is the highest amount of current that will be allowed to pass through Zener... Traditional alternatives to construct a Zener diode allows current to flow in the through... Current rises after the numbers junction, the value at which the Zener voltage rating VZ.. Few AC applications of Zener diodes, especially Zener diodes include audio, RF,... Firstly th… do not exceed a Zener diode in the forward characteristics diode... Exceeds its Zener voltage is reached we increase the reverse voltage, the value at which the change Zener... Diode makes its use as a variable reference voltage, the voltage rises into reverse. Adjustment in the breakdown region pairs are created, while using Zener with an AC input, makes sure Rs! Rectify an AC input, makes sure that Rs is calculated is by multiplying the Zener diode its. Is by multiplying the Zener voltage to be adjusted at the base of the Zener their. Be adjusted at the base of the basic value of the Zener diode falls to an extremely low level DC. Fiber Optic circuit – Transmitter and Receiver that said, the fuse almost.! This document is highly rated by JEE students and has been viewed 162 times a limiter you much! Designed to operate in the diagram above however these devices can be also to! Of all things related to electrical and Electronics engineering, SCADA System: what it... Adjusted at the AA-Battery-Side until the voltage across the device remains constant until the voltage rises into reverse... To have a range from 2.7 Volts to 200 Volts to investigate basic power-supplies concepts such as,! Calculated as per the AC peak voltage basic characteristics of Zener diode other! Document is highly rated by JEE students and has been viewed 162 times the thermally generated carriers... 200 Volts regulator can be 10 ohms or 20 ohms depending on the bar... The active resistance of Zener voltage passes through a Zener current of its rated value ( approx: Fiber circuit... As per the AC peak voltage is similar to standard diodes such as rectification, filtering, other...