This property of zener diode makes its use as a voltage regulator. Lab report experiment no 02 objectives to study the. Zener diode as a voltage regulator working principles. Zener diode as voltage regulator theory amrita virtual lab.
Voltage regulation 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. Link for the theoretical part of zener diode as voltage regulator. 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 clarence zener is the scientist who discovered this electrical property and the device is. In our previous articles, we explain in detail about diodes, pn junction diode, semiconductors etc. The line of text describes the properties of the model being using by pspice.
Mam can u please upload line regulator as well and half wave rectifier. Find the slope of the line from the linear part of the curve as shown in fig3a. Fig 3 circuit diagram of zener diode as line regulator. The reference voltage is provided by the zener diode and the transistor acts as.
Zener diode, resistor, variable dc power supply, milliammeter. In on state, the voltage across zener diode remains constant until the voltage across it deops less than vz. 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 parameter is is the saturation or scale current of the diode, as we have discussed in class it is has the typical default value of 1014 a. The zener diode has a unique property that offers a simple, lowcost solution to this problem.
Zener diodes as voltage regulators a circuit diagram symbol for a zener diode. The zener breakdown voltage is the minimum reverse biased voltage below which the diode blocks the reverse. Fig 4 circuit diagram of zener diode as load regulator. E ective v ripple mv peak v ripple mv calculated 12. When biased in the forward direction it behaves just like a normal signal diode, but when a reverse voltage is. Q 2 can be a 2n3904 and d 2, d 3 can be a 1n914 the extra diode d 2 is added in series with the zener to partially cancel the additional v be drop due to the emitter follower q 1. The zener diode mainly operates in reverse biased condition. V z0 is the voltage at which the straight line approximation of the iv characteristic intersects. Change the rheostat value from maximum to 0 by the interval 100. An example zener diode voltage regulation circuit is analyzed for its ability to regulate the voltage to a load while the source voltage changes.
To construct a zener diode voltage regulator and measure its line and load regulation. 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. We benefit hugely from resources on the web so we decided we should try and give back some of our knowledge and. Zener controlled transistor series voltage regulator the output of the rectifier that is filtered is then given to the input terminals and regulated output voltage vload is obtained across the load resistor rload. Zener diodes are used in circuits to maintain a fixed voltage across a load. As long as the external circuit connected to the diode limits the diode current to less than burn out value, the diode will not burn out. To setup and study a zener diode shunt regulator and to plot its line and load regulation characteristics. The critical parameter of this type of diodes is the zener breakdown voltage. In line regulation output voltage is regulated when the input voltage changes.
To study the forward and reverse bias characteristics of diode and zener diode. This entire exercise was to show why the zener diode is a lousy regulator. The load voltage must equal v z as long as the zener diode is in the reverse breakdown mode. Voltage regulation is classified into line regulation and load regulation. Load regulation z for voltage regulators, we typically define a load r l in terms of its current i l, where. V z0 is the voltage at which the straightline approximation of the iv characteristic intersects. The load voltage equals breakdown voltage vz of the diode.
The purpose of load regulation is regulating output voltage when theload changes. In a dc circuit, zener diode can be used as a voltage regulator or to provide voltage reference. Typically it is used for providing a stable reference voltage for use in power supplies and other equipment. The basic function of zener diode is to maintain a specific voltage across its terminals within given limits of line or load change. Any active device is going to cause the vout node to be unstable.
Identification of cathode when working with different types of diodes, it is also necessary to distinguish one end of the diode from the other anode from cathode. So the actual output voltage will be in the range of 10. The series resistor limits the current through the diode and drops the excess voltage when the diode is conducting. To study and draw the characteristics of rectifier filter circuit. The zener diode is used in its reverse bias or reverse breakdown mode, i. The zener diode working principles and its various. The voltage drop depends too much on the current flowing through the junction. Once the current starts increasing vary v s in steps of 1v up to 12v. Fix the load resistance value by using load resistance slider. 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. Now, since the zener diode in a shunt regulator has some. Zener diode characteristics and zener as voltage regulator. A semiconductor diode is prepared by joining p and n sections of a semi conducting.
Zener diode is a general purpose diode, which behaves like a normal diode when forward biased. The load regulation is not a fixed number but rather presented as a percentage. Analysis and measurement of a zener diode voltagereference. Build either of the circuits shown in figure 2 on your solderless breadboard using the 1n4735 6. Zener and resistor voltage were measured for the following combinations of e and r. 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. 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. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. We use zener diodes for voltage regulation and voltage stabilisation. To study the voltage regulation in zener diode regulation circuit. Characteristics of pn junction diodestatic and dynamic resistance.
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. They provide a lowcost and no frill method for voltage regulation. Zener diode as voltage regulator experiment youtube. The voltage drop across the zener diode and the load remains constant at 4. Can the line regulation of the discrete transistor regulators be improved by changing how the zener diode is connected to the circuits. Figure 4 a a zener diode voltage regulator circuit diagram. Zener diode is a pn junction diode specially designed to operate in.
I zener do you see any relationship between load current and zener diode current. Voltage regulation using zener diodes bryan witherspoon november 8, 2008 abstract in digital or mixedsignal applications, there is a need to precisely regulate the voltage entering or exiting a circuit. From the iv characteristics curve above, we can see that the zener diode has a region in its reverse bias characteristics of almost a constant negative voltage regardless of the value of the current flowing through the diode. This zener breakdown voltage on the iv curve is almost a vertical straight line. A typical zener diode shunt regulator is shown in figure 2. This was a bad thing before the whole avalanche breakdown, large current.
The zener regulator is composed of resistor r1 and zener diode. Zener diode as voltage regulator tutorial electronicstutorials. The power supply should be able to supply a constant and reliable power to within the specified load current range. The discrete transistor regulator load regulation curves re. Explain how zener diode maintains constant voltage across the load. Zener diode as voltage regulator theory circuit diagram. There are several ways of finding out this relation, but the most systematic one, that can be applied the same way to all circuits, is the smallsignal analysis. Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits. Three observations are sufficient to understand the operation of this voltage regulator. The main use of zener diode lies in the fact that the voltage across a zener diode remains constant for a larger change in current.
The zener diode is like a generalpurpose signal diode. We ignore the resistance of the diode, r d, calculated as r d dv ddi1, in writing kirchhoffs voltage law. Zener diode is a special kind of diode which permits the flow of current in the forward direction as well as in reverse direction when the voltage is above a certain voltage known as breakdown or zener voltage. Zener diode, resistors, power supply, multi meter circuit diagram. Construction of zener zener diodes are designed to operate in reverse breakdown. Select and place the zener diode part d1n750 in your circuit. The zener breakdown voltage is the minimum reverse biased voltage below which the diode blocks the reverse current. Contents1 line regulation2 load regulation 3 linear and switching voltage regulator3. Zener diode makes for a lousy regulator bald engineer. Resistor value and circuit example sought for zener diode voltage protection.
The electric field may become large enough that covalent bonds are broken and electronhole pairs are created. Zener diode, resistor, variable dc power supply, milliammeter, voltmeter, rheostat and wire. Experiment data this section consists of both the expected and measured experiment results of the zener and regulator power supplies. Which means the regulator circuit, depends on a constant load.
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