This current flows due to the thermally generated minority carriers. Apparatus:-Experimental kit and patch cords. Fig 2: Zener diode characteristic curve . We will build the zener diode circuit and zener diode circuit with load from Figure 5.1 (See Appendix) and Figure 5.2 (See Appendix) in lab and will observe and record the experimental values. This sudden and sharp increase in zener current is called as zener breakdown. 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. The breakdown voltage in case of zener diode is sharp. However, above an extent the temperature may have some affect on the device as indicated in the graph below: It shows the zener diode temperature coefficient curve. When we apply a voltage more than the Zener breakdown voltage (can range from 1.2 volts to 200 volts), the depletion region vanishes, and large current starts to flow through the junction. We need to connect the circuit as given in the diagram above. The following graph shows the effect of the capacitor for reducing zener diode noise. Record your data in table and plot your results for the corresponding zener current on the graph You should notice that as the voltage drop approaches the diode's breakdown voltage, the diode's current increases rapidly, while at the same time the voltage stays nearly constant. Excellent regulation could be achieved from the above design using a 1k series resistor. In reverse bias, a negligible constant current flow through the zener diode but the current becomes abruptly large at certain voltage. This results in the relay switching ON in sequence as desired by the application. As a result the emitter voltage is maintained between a few tenths of a volt of the transistor base voltage as created by the Zener diode. Typical diodes have a very high reverse breakdown voltage, the voltage at which the diode begins to conduct in the reverse direction. A standard 10 V Zener may have a temperature coefficient of +0.07%/ °C which may correspond to 7 mV/ °C variation in temperature. Figure 2 shows the current versus voltage curve for a Zener diode. Ohms (!'fax. ) Diodes . If you have any circuit related query, you may interact through comments, I'll be most happy to help! Under these conditions, the zener diode will dissipate a power of Iz x Vz = 48.66 x 4.7 = 228 mW. The zener diode is sharply doped while the conventional diode is moderately doped. Zener diodes found its use in several applications. Different Zener diodes have a different breakdown voltage. In most circuit applications this may work as effectively as a typical smoothing capacitor having several thousand microfarads capacity, resulting in a significant reduction in the level of ripple voltage superimposed on the DC output. To study the voltage regulation in Zener diode regulation circuit. Do the same experiment by connecting the Zener diode in the forward bias. Unlike ordinary PN junction diode, the reverse current in Zener diode is measured using milli-ammeter due to the large flow of current. Distinctive material, useful read. We will see that the voltage across the diode remains constant whereas the current through it keeps on increasing. Why should we do this experiment? Not Specified Not Specified The function of CR1 is to provide additional regulation of the input voltage and form the basis of the reference output. They provide a low-cost and no frill method for voltage regulation. FORMULA. Note down this voltage separately. Measure the value of VL and VR. Apparatus A Zener diode (with small reverse breakdown voltage of about 6 volts), [i.e., V z = 6 V], a ten volt battery, a high resistance rheostat, two 0-10 V voltmeter, one 0-100 mA ammeter, one 20 Ω. resistance, one way key, connecting wires. A Zener diode not only allows current to flow from anode to cathode but also, in the reverse direction on reaching the Zener voltage. The I-V Characteristics Curve of a zener diode, shown below, is the curve which shows the current-voltage relationship of a zener diode. Zener diodes are designed in many wattage ratings and with voltage ratings which range from 2.7 Volts to 200 Volts. ... For higher values of Zener voltage, TC is positive d) All of the mentioned. Thank you Andrew, Glad you are loving my site, you can find the required details under this category: https://www.homemade-circuits.com/category/electronic-devices-and-circuit-theory/page/4/, https://www.homemade-circuits.com/category/electronic-devices-and-circuit-theory/page/3/. A Zener diode is a 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 This adjustment in the resistance of the transistor results in an automatic correction of the output current to the desired level. A zener diode is a silicon pn junction device that is designed for operation in the reverse-breakdown region. 20 . 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 typical value of V BE ... Zener diode is a P-N junction diode specially designed to operate in the reverse biased mode. Here Vz is the Zener breakdown voltage. Previous: Calculating Transistor as a Switch, Next: Fiber Optic Circuit – Transmitter and Receiver. When power is switched ON, the zener diodes conduct one after the other in sequence in an increasing order of their zener values. Objectives: To study the characteristics of Zener diode. But in normal PN junction diodes, the breakdown voltage is comparatively high This can be suppressed by adding a capacitor in parallel with the zener diode, as shown below: The value of the capacitor can be between 0.01uF and 0.1uF, which will allow noise suppression by a factor of 10, and will maintain the best possible voltage stabilization. Please see the following example schematic for the same. Hence we can use Zener diode for voltage regulation. In this situation, suppose the input voltage increases to an extent that exceeds the Zener breakdown voltage - will force the Zener diode to conduct. Externally, you may find zener diodes a lot similar to standard diodes such as 1N4148. This was conducted as an introductory to Electronics laboratory and in line with some topics in lecture classes. Plot the reverse characteristic curve by taking reverse voltage along –ve X-axis and reverse current along –ve Y-axis. Keep increasing the reverse bias voltage further. Figure . 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. Zener Diode characteristics: VI characteristics of Zener Diode. A single zener diode would limit the swing in one direction only. 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. 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. Note down the voltmeter reading at this point. General values for working zener knee voltage are 5.1 V, 6.2 V, 15 V and so on. This will cause a sudden increase in the current blowing the fuse almost instantaneously. Course. 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. The diagram shows a bridge network built using a pair of resistors and a pair of Zener diodes having identical characteristics. The above is the maximum current that will be allowed to pass through the zener diode. To plot Volt-Ampere characteristics of Zener diode. Zener Diode Code Identification: Zener Diodes have an additional letter which will appear after the numbers. Zener diodes - named after its inventor Dr. Carl Zener are fundamentally used in electronic circuits for generating precise voltage references. The above diagram shows the V-I characteristics of the Zener diode. For even better results, a series pass transistor type of regulator as shown below looks a better option and preferable. 3. Note down the current and voltage reading. Academic year. The experiment is fairly simple to perform. Ex: 5V1 indicate 5.1V To find Zener break down voltage in reverse biased condition. You will get the characteristic curve of Zener diode. Required Equipment • Experiment Module: PC BASIC ELECTRONIC BOARD, Type 1017.1 USB. Fig 2:Zener diode characteristic curve The forward bias region of a Zener diode is identical to that of a regular diode. The graph of voltage vs current of a diode is called its characteristic. 40 mA). Determine the maximum and minimum load current (Li), for example 10 mA and 0 mA. The P type has excess number of holes while the N type has excess number of electrons. The Zener diode mainly operates in reverse biased condition. Therefore, applying Ohm's law we get Iz = 12 - 4.7 / 150 = 48.66 mA. Zener Diode Characteristics - Zener regulator Prelab: You are tasked to determine experimentally the characteristic curve of a reverse-biased Zener diode. But sir, am a beginner in electronics, and am looking for how a transistor functions in different configurations, including CB, CC, CE mode. 3 Theory of experiment The diode is a device formed from a junction of n-type and p-type semiconductor material. ZENER DIODE CHARACTERISTICS . A zener diode when forward biased behaves like an ordinary P-N junction diode. The typical forward voltage at room temperature with a current of around 1 mA is around 0.6 volts. Zeners diodes are normally used with DC supplies, however these devices can be also designed to work with AC supplies. A standard voltage regulator circuit, using a single resistor and a Zener diode, can be witnessed in the following image. 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 zener voltage ratings of the individual zener diodes should be best chosen for most of the applications. The symbol of zener diode is similar to the normal p-n junction diode, but with bend edges on the vertical bar. The main aim of this experiment lies in to find out the basic value of the Zener voltage. Zener diodes are designed in a way where the Zener voltage is a much lower value. If you keep doing so, after a particular value of reverse bias voltage, the value of current in A1 will spike suddenly. Record the measured value of each resistor. Which is in A, will follow. 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. For that, we increase the reverse bias voltage slowly and in small steps. This property of zener diode makes its use as a voltage regulator. 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. 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? Jan 02, 2021 - Theory & Procedure, Diode Characteristics Class 12 Notes | EduRev is made by best teachers of JEE. 11 CONCLUSION Experimentally, throughout this experiment, we can see that the characteristics of junction diode, Zener diode and also the light emitting diode almost fits the theoretical facts. We should select a Zener diode with a breakdown voltage approximately equal to the voltage we need across the device. A zener diode Conducts excellently even in reverse biased condition. In general, the cathode of a diode is marked by a solid line on the diode.The These are devices that are able to create a practically constant voltage across them regardless of variations in circuit and voltage situations. Zener diodes are heavily doped than ordinary diodes. VOLTAGE-CURRENT CHARACTERISTICS OF A ZENER DIODE . Figure 4 shows a case in which reverse-bias breakdown of zener diodes limit the voltage swing across the load resistor. Adding a shunt transistor not only enhances the zener power handling capacity by a factor of 10, it further improves the voltage regulation level of the output, which may be as high as the specified current gain of the transistor. PS: How are you? Experiment No.4 Zener diode Characteristics Object: To study and measure the effects of forward and reverse bias on the zener diode current. This article will help to explain the characteristics which make up zener diodes, specifically how the voltage across a zener diode varies with the current flowing through it. 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. Apparatus A Zener diode (with small reverse breakdown voltage of about 6 volts), [i.e., V z = 6 V], a ten volt battery, a high resistance rheostat, two 0-10 V voltmeter, one 0-100 mA ammeter, one 20 Ω. resistance, one way key, connecting wires. Zener diodes can be also applied as effective ripple voltage filters, just as it's used for AC voltage stabilization. In simple words, whenever the supply across the zener diode exceeds the rated zener value, the zener diode conducts and grounds the excess voltage. However, the Zener Diode or Breakdown Diode, as they are sometimes referred too, are basically the same as the standard PN junction diode but they are specially designed to have a low and specified Reverse Breakdown Voltage which takes advantage of any reverse voltage applied to it. Circuit Theory (EE112) Uploaded by. (However mostly , Zener diodes with values far above 30 Volts are hardly ever used.) 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). Do not exceed a zener current of its rated value (approx. By connecting the negative terminal of the battery to the diode anode terminal, zener diode starts operating in the reverse bias or breakdown mode. A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" when a certain set reverse voltage, known as the Zener voltage, is reached.. Zener diodes are manufactured with a great variety of Zener voltages and some are even variable. Zener breakdown voltage should be approximately close to the desired voltage we want. As a result Zener diodes are often used for getting a constant voltage drop, or reference voltage, with their internal resistance. Instead, the fuse blows only when the voltage and current genuinely rises beyond a specified unsafe level. Zener Diode 62 4 < 125 < 2000 < 5 47.1 1N4759A 1) Based on DC-measurement at thermal equilibrium while maintaining the lead ... (3/8 inches) from the diode body. The symbol for a zener diode is shown in Below Figure. Different Zener diodes have a different breakdown voltage. The breakdown voltage in case of zener diode is sharp. Part I : VI Characteristics of zener diodes . VDC +2 . To investigate basic power-supplies concepts such as rectification, filtering, and regulation. As the voltage rises into e reverse direction, initially very little current flows. 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. Therefore, if 180 V is assumed to be the low voltage cut off threshold, then selecting the zener diode as a 10 V device will cut off the relay operation whenever the input AC drops below 180 V. I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. This is an individual effort but members of a team can and should share insight, confirm results, and help problem solve. That said, the design is rather inefficient because the transistor may dissipate a significant amount of current in the absence of a load. We are going to learn about an experiment to find out the Zener breakdown voltage and draw the characteristics of Zener diode. The vi characteristics of a zener diode is shown in the below figure. Although zener diodes provide a quick and easy way to create stabilized fixed voltage outputs, it has one drawback which may affect sensitive audio circuits such as power amplifiers. 3 Theory of experiment A Zener Diode is constructed for operation in the reverse breakdown re-gion.The relation between I-V is almost linear in this case V z = V z0 +I zr z, where r z is the dynamic resistance of the zener at the operating point.V z0 is the voltage at which the straight-line approximation of the I-V characteristic intersects the horizontal axis. Because, the signal is negative therefore the AC will be shorted via the anode to cathode of the zener, causing 0 V to appear the output. 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. Here we go with the Zener Diode Characteristics Experiment Using Multisim Software Zener diode has the property of behaving like a dc battery in ‘on’ state (i.e. Firstly th… This document is highly rated by JEE students and has been viewed 162 times. The Zener diode is rated at 400 mW, and the minimum Zener current is 5mA. The voltage at this value is the Zener breakdown voltage. AIM. First, we will plot the curve in reverse biased mode. Here, the voltage must be same as the ripple trough level. However, this modification may result in a lower regulation efficiency due to some shunting effect created by the potentiometer. EXPERIMENT: DIODE & ZENER DIODE Objective:- To study the forward and reverse bias characteristics of diode and zener diode. 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. Experiment No: 2 ZENER DIODE CHARACTERISTICS AIM: 1. Populate the values in the table. This level starts just under the 'knee' of the reverse voltage/reverse current curve as learned from the previous graphical diagram above. (However mostly , Zener diodes with values far above 30 Volts are hardly ever used.). 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.

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