Zener diodes this worksheet and all related files are licensed under. Career point cares zener diodes are a special kind of diode which permits current to flow in the forward direction. Please login if you have an account or else signup. The zener diode voltage regulator is based on a particular characteristic of zener diodes. Zener diodes are simple and useful devices for building voltage regulator circuits, but are times when you may have to improvise in the absence of the proper zener diode. Establish the concept of voltage reference voltage regulator analyze the voltage regulator with the zener diode become familiar with three major rectifier types.
Never touch the probes to a voltage source when a test lead is plugged into the 10 a or 300 ma input jack. Exploiting this characteristic of zener diodes allows for simple, inexpensive voltage regulators. Draw the reverse characteristics of zener diode and determine its break down voltage. The stabilised output voltage is always selected to be the same as the breakdown voltage v z of the diode. So i am very curious why a zener diode a regular npn transistor and a mosfet transistor could not be used as a switching regulator. The zener diode varies in a wider range based on its mounting location.
I guess you already know that a diode acts as a oneway passage of electricity. Where rload should get whatever voltage is across the 1n4001 or whatever diode. Zener diode as a voltage regulator working principles byjus. The aim of the laboratory work is to understand the principle of zener diode operation and also apply the knowledge practically by completing laboratory tasks. The exciting part of this diode is that we can choose the zener diode with a suitable breakdown voltage to work as a voltage regulator in our circuit. These devices are designed to provide voltage regulation with minimum space requirement. Following was given for forward bias of the diode quoting from the text, if the power supply voltage were to be increased.
Repeat steps 2 through 6 using a 7812 voltage regulator instead of a zener diode. Zener diode is a pn junction diode specially designed to operate in. The very simple zener diode circuit providing the shunt regulator function as shown above is not particularly efficient and is not practicable for many higher current applications. Aug 23, 2016 in this video, we show how to build a voltage regulator with a zener diode. Voltage regulator a zener diode can be applied in a voltage regulator circuit to regulate the voltage applied to a load, such as in a linear regulator. Ee200 circuit laboratory 20192020 5 study zener diode characteristics from the document named zener diode. Plot the graph in which v in at xaxis v l at yaxis. Zener diodes are used in voltage regulation in circuits because even. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diodes reverse breakdown voltage. Zener diodes are simple and useful devices for building voltage regulator circuits, but are times when.
Feb 23, 2017 zener diode is a reverse biased heavily doped semiconductor silicon or germanium pn junction diode, which is operated exclusively in the breakdown region. Take care not to exceed the power rating of your series resistor. With your lab partner, brainstorm on the following ideas. The excess voltage required for reversing the direction of flow of current is termed as breakdown voltage or zener voltage. Zener diode is a general purpose diode, which behaves like a normal diode when forward biased. How do you construct the laboratory experiment that will allow you to make this.
As shown in the figure above, the resistor is selected so that when the input voltage v in is minimum and the load current i l is maximum than the current through the zener diode is, at least, minimum i z. Regular not zener diode as voltage regulator electrical. The major role of a zener diode is to function as a voltage regulator. The zener voltage regulator consists of a current limiting resistor r s connected in series with the input voltage v s with the zener diode connected in parallel with the load r l in this reverse biased condition. Zener diodes voltage regulator, diodes clippers and clampers. You are tasked to determine experimentally the characteristic curve of a reversebiased zener diode. The dc output voltage remains constant when the input varies within the limits as voltage regulator is used. Calculate the e ective voltage and ripple voltage across the load. There are several drawbacks, however, that will be discussed shortly. The circuit could be arranged in such a way that the diode would allow voltage in excess of its nominal vz into the gate of the npn transistor. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diode s reverse breakdown voltage. Hi, i was reading up on the the zener diode on the website.
Study zener diode applications such as clipper, voltage regulator etc. Pdf performance of shunt voltage regulators based on zener. This section consists of both the expected and measured experiment results of the zener and regulator power supplies. To avoid damage or injury, never use the meter on circuits that exceed 4800 watts. Calculate the peak voltage and ripple voltage across the recti er output lter capacitor. To connect a zener diode in a circuit to provide voltage regulation, the zener diode should be connected, in reverse biased, in parallel to the power. This is the main reason behind using zener diode as a voltage regulator. To see the full detail of this circuit, including the schematic diagram, see. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. In this part, limiting circuit is described in figure 1 above. The breakdown voltage or zener voltage v z across the diode remains relatively constant. For example, we want that the voltage across a load in our circuit does not exceed, lets say, 12 volts. To plot and study the input and output characteristics of bjt in. This was a bad thing before the whole avalanche breakdown, large current.
This circuit lowers the output voltage by zener diode as a quantity that is equal to the zener voltage shifter diodes breakdown voltage. A zener diode is a diode that breaks down at a specific voltage when it is reverse biased. Jan 02, 2019 the exciting part of this diode is that we can choose the zener diode with a suitable breakdown voltage to work as a voltage regulator in our circuit. Zener diode, resistors, power supply, multi meter circuit diagram. In on state, the voltage across zener diode remains constant until the voltage across it deops less than vz. When the zener diode is operated in the breakdown or zener region, the voltage across it is substantially constant for a large change of current through it. Observation of characteristics of a zener diode debangshu mukherjee bs. Zener diode characteristics zener regulator prelab. The first equation that you have is the voltage divider equation that is solved for rsmax because the other three values are known. 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.
Dec 14, 2012 zener diode is a general purpose diode, which behaves like a normal diode when forward biased. Zener diode has the property of behaving like a dc battery in on state i. Read on to understand how zener diodes and resistors are matched for any particular scenario. When zener diodes are used as voltage regulators, there is a range of current that the load can draw and still maintain regulation on one end while keeping zener diode power dissipation below the. In the case of normal diodes the diode damages at the break down voltage. Zener diode as a voltage regulator, where do the formulas. In normal diodes, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied as the reverse voltage applied to the zener diode increases towards the. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. Zener diode characteristics and zener as voltage regulator. Zener diode as a voltage regulator zener diode is a silicon semiconductor with a pn junction that is specifically designed to work in the reverse biased condition. The zener diode specially made to have a reverse voltage breakdown at a specific voltage. The collector of the npn could be wired to the gate of the mosfet. In this video, we show how to build a voltage regulator with a zener diode. While very high quality voltage regulators are available in integrated circuits, at times it may be sufficient and convenient to use a simple zener.
Fix the load resistance value by using load resistance slider. Nov 08, 2008 with an ideal zener diode, construction of a voltage regulator is easy, simply connect the diode between the unregulated voltage and ground. This breakdown voltage is known as the zener voltage. Applications of zener diodes zener diodes finds a wide applications commercially and industrially. University of north carolina at charlotte department of. For any given output voltage and current requirement it will calculate the value of power rating of the current limiting resistor and zener diode. Some of the important applications of a zener diodes are as a voltage regulator or stabilizer, as a meter protector and as a wave shaper. The output voltage of regulator system is fixed as the zener knee voltage of the zener diode and can be used in power devices requiring a fixed voltage of firm value. Zener diode as a voltage regula tor zener diode is a silicon semiconductor with a pn junction that is specifically designed to work in the reverse biased condition. In this tutorial, we will examine the use of zener diode in pspice and learn about editing the properties of devices this tutorial is written with the assumption that you know how to do all of the basic things in.
Zener diodes are used in circuits to maintain a fixed voltage across a load. The idea is that rl is using all of the available current and the zener diode is not conducting at all. But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a. Study of zener diode as a voltage regulator diode volt scribd. Zener diodes when we first talked about practical diodes, it was mentioned that a parameter associated with the diode in the reverse bias region was the breakdown voltage, v br, also known as the peakinverse voltage piv. Zener diode as a voltage regulator a voltage regulator is an electronic circuit that provides a stable dc voltage independent of the load current, temperature and ac line voltage variations. If you dont have an exact values above such as dc voltage or the exact zener diode, experiment with other components, you just have to make sure that you have a voltage that is higher than the breakdown voltage of the zener diode, you can use your digital tester to measure the. Change the rheostat value from maximum to 0 by the interval 100. We are going to learn about an experiment to find out the zener breakdown voltage and draw the characteristics of zener diode. If the zener current is zero then it follows that the circuit is a simple voltage divider. Zener diode as voltage regulator tutorials on semiconductor.
How to build a voltage regulator with a zener diode youtube. Building a voltage regulator with an ideal zener diode, construction of a voltage regulator is easy, simply connect the diode between the unregulated voltage and ground. Zener diode makes for a lousy regulator bald engineer. The circuit consists of an npn transistor and a zener diode along with a series resistor rseries that is connected in series with the input supply. A zener diode of break down voltage v z is reverse connected to an input voltage source v i across a load resistance r l and a series resistor r s. It is fairly employed in many electrical and electronic tools and equipments.
Building a voltage regulator with an ideal zener diode, construction of a voltage regulator is easy, simply connect the diode between. The prelab and postlab report format is as follows. It allows the current to flow as like a normal pn junction diode when it is forward biased and block the reverse flow of current during the reverse bias up to the breakdown voltage. Note down the corresponding input voltage and output voltage and tabulate it. What would be the potential drawbacks of using something like this on the picture below. It is different from others diodes zener diodes will also allow current to flow in the reverse direction when the voltage is above a certain value. Zener diodes are rated by their breakdown voltage v z and maximum power p z typically 400mw or 1. The voltage drop of the diode is approximately equal to the transistor base emitter voltage. Get same day shipping, find new products every month, and feel confident with our low price guarantee. Zener diodes as voltage regulators a circuit diagram symbol for a zener diode.
The purpose of a voltage regulator is to maintain a constant voltage across a load regardless of variations in the applied input voltage and variations in the load current. Applications of zener diodes voltage regulator, meter. But it is not the universal solution for the voltage regulation in this short post we will discuss in brief about various voltage regulator circuits it is recommended to read about how zener diode will provide the voltage regulation in the circuit before proceeding. Voltage regulation in the circuit means zener diode will come in our mind. Zener diode as voltage regulator and its vi characteristics. In this post, we will see how to design the zener shunt regulator. Zener diode shunt regulator shunt regulators are normally only used for applications where the load power is not much often only milliwatts and rarely more than a few hundred milliwatts because under the worst case situation of no load the zener has to dissipate the full load power. Sep 12, 2015 the output voltage of regulator system is fixed as the zener knee voltage of the zener diode and can be used in power devices requiring a fixed voltage of firm value.
Keep the multisim file handy to refer it to in the lab. Never apply more than the rated voltage between any input jack and earth ground 600 v for the fluke 73. On the other hand an ic voltage regulator draws from power source a bias current which is almost constant regardless of the load and input voltage and in most cases is. The zener diode working principles and its various applications. Zener diode as a voltage regulator working principles. A voltage regulator is an electronic circuit that provides a stable dc voltage independent of the load current, temperature and ac line voltage variations. The zener diode working principles and its various. In figure 51, an often used zener diode voltage regulator is shown. To design series and shunt voltage regulator experiment 11. Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. Zener diode working, characteristics and application as. I see a lot of information regarding zener diode voltage regulators but how about a regular diode voltage regulator. The low value is required so as to allow the maximum flow of current through the diode, connected in parallel. They are well suited for applications such as cellular phones, hand held portables, and high density pc boards.
It is acting as normal diode while forward biasing. Diodes which are designed with adequate power dissipation capabilities to operate in the break down region are called as break down or zener diodes. Since the exploited property of zener diodes is the reverse breakdown voltage, connect the anode of the diode to ground, not the cathode. This series of zener diodes is offered in the convenient, surface mount plastic sot23 package. The function of a voltage regulator is to provide a constant low ripple output voltage under varying load current conditions. The vi characteristic of zener diode indicates that characteristic of zener diode in forward bias is same as pn junction diode. The zener diode is a type of diode which operates under the reverse bias that breakdowns when the applied voltage reaches a particular reverse bias voltage or knee voltage. The zener diode regulator of figure 1 offers a very simplified way to maintain the load voltage v l at the same value as the reverse breakdown voltage of the zener diode, provided that the load resistance r l remains higher than some lower limit. Study of zener diode as a voltage regulator free download as pdf file. Zener breakdown voltage should be approximately close to the desired voltage we want.
But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a wide range of current. The purpose of this experiment is to investigate the application of a zener diode for voltage regulation and also diode applications in clipping and clamping circuits. Whats the difference between the voltage regulators and. This simple zener diode circuit is widely used as an easy method of providing a voltage reference. A simple circuit involving zener diode as a regulator requires a resistor of low value connected in series with the input voltage source. Regulator zener diode regulator for low current power supplies a simple voltage regulator can be made with a resistor and a zener diode connected in reverse. For correct voltage regulation, we need to find out precisely what voltage should be across the zener diode. The zener diode will maintain a steady, constant voltage of 5. It will allow current to flow in a particular direction forward bias but it will prevent current to flow in the reverse direction reverse bias. The zener diode will continue in regulating the voltage till the zener diode current falls below the minimum i z min value in the reverse breakdown region.
One of the simple linear power supply is the zener shunt regulator. In this experiment, we try to observe the relation between the voltage and. May 10, 2016 career point cares hence with the help above given facts and the simulation on proteous software correctly it is clear that above circuit for working of zener diode as a voltage regulator is fully correct and is working properly. Zener diode voltage regulator calculator below is a simple to use zener diode voltage regulator calculator. Zener controlled transistor shunt voltage regulator the image below shows the circuit diagram of a shunt voltage regulator. A zener diode is a very useful device for regulating voltage. Explain how normal diodes might be used as crude substitutes for a zener diode in the following circuit. By connecting it in the right way in a circuit, it can act as a voltage regulator, to regulate how much voltage it feeds to a device. In reverse bias, a negligible constant current flow through the zener diode but the current becomes abruptly large at certain voltage. When forward biased, it behaves like a normal signal diode, but when the reverse voltage is applied to it, the voltage remains constant for a wide range of currents. The zener diode is connected across the base and the. Zener diode circuit for psu with series transistor.