A simple Zener-regulated constant current supply can be designed through a single transistor as a variable series resistor. We will see that the voltage across the diode remains constant whereas the current through it keeps on increasing. The graph of voltage vs current of a diode is called its characteristic. To draw the characteristic curve of a Zener diode and to determine its reverse 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. 2019/2020 The critical parameter of this type of diodes is the Zener breakdown voltage. FORMULA. For that, we increase the reverse bias voltage slowly and in small steps. The Zener diode is a unique device which exploits a property of diodes that is generally avoided in standard diode applications. 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. In simple words, whenever the supply across the zener diode exceeds the rated zener value, the zener diode conducts and grounds the excess voltage. This was conducted as an introductory to Electronics laboratory and in line with some topics in lecture classes. Previous: Calculating Transistor as a Switch, Next: Fiber Optic Circuit – Transmitter and Receiver. Note down this voltage separately. To plot Volt-Ampere characteristics of Zener diode. shapely quest. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. PS: How are you? However, this modification may result in a lower regulation efficiency due to some shunting effect created by the potentiometer. Reverse Characteristics. Observe the nearly constant voltage in the breakdown region. Zener Diode Definition Zener Diode Working Zener Diode Circuit Symbol VI Characteristics of Zener Diode Zener Diode Applications FAQs. 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. Zener diodes are designed in many wattage ratings and with voltage ratings which range from 2.7 Volts to 200 Volts. Your table should look something like the one shown above. (However mostly , Zener diodes with values far above 30 Volts are hardly ever used.) Unlike ordinary PN junction diode, the reverse current in Zener diode is measured using milli-ammeter due to the large flow of current. While doing so, keep noting down the ammeter reading and the voltmeter reading. The Zener breakdown voltage is the minimum reverse biased voltage below which the diode blocks the reverse current through it and above which it causes a significant amount of reverse bias current to flow through it. 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/. The break down voltage Vz is obtained from the graph as shown below. The voltmeter reading is the Zener breakdown voltage. 3. The voltage at this value is the Zener breakdown voltage. But sir, am a beginner in electronics, and am looking for how a transistor functions in different configurations, including CB, CC, CE mode. The main aim of this experiment lies in to find out the basic value of the Zener voltage. Instead, the fuse blows only when the voltage and current genuinely rises beyond a specified unsafe level. Zener Diode Characteristics - Zener regulator Prelab: You are tasked to determine experimentally the characteristic curve of a reverse-biased Zener diode. In zener diode, electric current flows from both anode to cathode and cathode to anode. If you continue to use this site we will assume that you are happy with it. 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). Very useful for zener diode circuit explained thank you sir, sir 350 w,ir2153 ic smps power supply short circuit protection,how to add the circuit please sent circuit diagram sir, thank you. Remember, while using zener with an AC input, makes sure that Rs is calculated as per the AC peak voltage. The electric field may become large enough that covalent bonds are broken and electron-hole pairs are created. The experiment is continued till the milliammeter shows a large deflection while the voltmeter reading remains a constant, indicating the break down voltage. UCSI University. Externally, you may find zener diodes a lot similar to standard diodes such as 1N4148. Apparatus:-Experimental kit and patch cords. Zener diodes found its use in several applications. Academic year. 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. Figure . These are devices that are able to create a practically constant voltage across them regardless of variations in circuit and voltage situations. 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. This is typically 0.6 volts for silicon diodes - virtually all Zener diodes are silicon diodes. This is an individual effort but members of a team can and should share insight, confirm results, and help problem solve. Firstly th… 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. To draw the voltage-current (V-I) characteristic curves of a Zener diode and to determine its knee voltage, forward resistance and reverse breakdown voltage. Once the values are found it should be plotted as characteristics curve. This current flows due to the thermally generated minority carriers. In this circuit the Zener diode creates a reference voltage for the series pass transistor, which, essentially, works like an emitter follower. The list of the componentsof equipment required to perform this experiment mainly include Zener diode, Milliammeter, Voltmeter, and DC supply(variable), and Resistors 1. Do not exceed a zener current of its rated value (approx. For the experiment, we will follow the below circuit diagram. If you have an application where a set of relays are required to be switched sequentially one after the other on power switch instead of all activating together, then the following design can prove quite handy. The experiment is fairly simple to perform. Excellent regulation could be achieved from the above design using a 1k series resistor. As we increase the reverse voltage, initially a small reverse saturation current Io. Zener effect dominates at reverse voltages less than 5 volt whereas avalanche effect dominates above 5 V. The typical forward voltage at room temperature with a current of around 1 mA is around 0.6 volts. 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