The basic construction of the Zener Diode is not different from the simple PN junction diode in a way that both diodes have an N-Region and P-Region and a PN junction. (Hons) It is also … It is majorly used in voltage regulation in order to keep the voltage constant even when the load shows variation. … The figure given below represents the symbol of a Zener diode: Its symbol is somewhat similar to the symbol of a normal diode. In Zener diodes with wider depletion layers and therefore higher breakdown voltages, the increase in current at the breakdown voltage is much more sudden, giving an abrupt reduction in the reverse resistance of the diode and a nearly vertical region to the diode´s reverse current characteristic. The Zener diode maintains a stable output voltage irrespective of the input voltage provided the … This device is a combination of P-type and N-type semiconductor material hence it is also known as PN … The actual breakdown voltage is controlled during manufacture by adjusting the amount of doping used. Practical zener diodes may use either the zener effect or the avalanche effect and in some diodes both effects can also occur at the same time, but it is common practice to call all these diodes zener diodes. • Describe the Avalanche effect in Zener Diodes. It is mainly a special property of the diode rather than any special type of equipment. The only … Zener diodes are also useful for providing an accurate reference voltage for purposes such as waveform clamping. A zener diode is like an ordinary diode only that it has been doped to have a sharp a breakdown voltage. The thickness of this … Zener diode regulators provide a constant output voltage despite changes in the input voltage or output current. Special techniques are applied in the fabrication of zener diodes to create the required properties. 2.4.1, this results in a relatively thin junction layer, and consequently a reverse breakdown voltage that can be much lower than in a conventional diode. In this accelerated state they begin to collide with other atoms and knock electrons from their atomic bonds in a process called ‘impact ionisation’, so creating more electron/hole pairs that are also greatly accelerated by the electric field. As shown in Fig. A Zener Diode, also known as a breakdown diode, is a heavily doped … Thus, a small increase in reverse voltage will cause an immediate increase in current through the device. Few applications of diodes are rectification, … Construction of zener diode. However, the reason for this is some external circuit is required in order to protect the device from the excess current. Zener Diode Explanation. A properly doped PN junction diode, which has a sharp breakdown, is known as a zener diode. As the reverse voltage approaches the reverse breakdown voltage the electrons and holes entering the depletion layer come under the effect of a strong electric field and are rapidly accelerated. Your email address will not be published. The depletion region formed in the diode is very thin (<1 µm) and the electric field is consequently very high (about 500 kV/m) even for a small reverse bias voltage of about 5 V, allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material. Definition: A special type of PN junction diode that operates in reverse biased mode, more specifically in breakdown region is known as Zener Diode. Due to this, more current flows through a zener diode as compared to a normal junction diode. However, a small variation is seen in the symbol of a zener diode which is shown by the bends at the two ends of the vertical line. The special property of the diode is that there will be a breakdown in the circuit if the voltage applied across a reversely biased circuit. October 6, 2017. in Articles. Reverse saturation current: It is the current flowing through the device at reverse biased condition due to the flow of minority charge carriers. Due to the … It is defined as the ratio of small change in zener voltage and current. Construction of Zener diode There are various methods which are used for manufacturing Zener diodes such as diffused structure, diffused and passivated structure and alloy diffused structure. Among numerous uses, let us discuss some crucial applications of zener diode: Zener voltage: It is that reverse bias voltage at the which junction breakdown completely and large current flows through the device at a constant potential. On increasing the reverse voltage, current increases. The P type and N type silicon used is doped more heavily than a standard PN diode. (Revision 15.00 29th December 2020). 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. Construction of Varactor Diode It is formed of P-type and N-type semiconductor and reverse biasing is applied to it. When a zener diode operates in the breakdown region, it does not burn rapidly. With the increase in reverse potential, a strong electric field is generated by the depletion region. Breakdown voltages can be selected in this way to occur at preci… As we already know that in reverse biased condition, small minority current flows through a normal diode. This effect happens mainly in diodes with a higher reverse breakdown voltage (above about 5V) and less heavily doped P and N regions. That means a large majority current flows through the device when the forward potential is applied to it. A point is reached when the junction gets destroyed and a sharp increase in current is noticed without any noticeable increase in reverse potential. Zener diodes are a modified form of PN silicon diode used extensively for voltage regulation. Diode construction follows a few very basic guidelines. We go over the characteristics & working principle of a Zener Diode. This breakdown mechanism is noticed in diodes that are heavily doped. Newest unlock from SMI with identify SMD Zener Diode Marketplace Analysis Document 2019-2026 (by way of Product Sort, Finish-Consumer / Utility and Areas / Nations) supplies an in … Zener breakdown was first noticed and explained by American Scientist C. Zener. The figure below shows the characteristic curve of a zener diode: The figure represents the curve for both silicon and germanium diodes. To determine … The construction of this diode is similar to the Zener diode, except doping level in this diode changes from Zener diode. At the same time during construction, the whole assembly is metallised in order to generate anode and cathode connection. So, we can conclude that a zener diode is definitely a reverse bias device. When they are reverse biased they exhibit a very high resistance, and consequently a low value of reverse leakage current. • Calculate appropriate values for current limiting resistors for Zener Diodes. As it resembles a normal diode in the forward biased region. The junction region is covered with a layer of silicon dioxide (SiO 2 ). It specifically acts in the breakdown region in the reverse biased condition. For practical reasons this current can be considered zero. After studying this section, you should be able to: • Describe typical Zener Diode construction. This effect is very useful in voltage regulator circuits, as explained in our Power Supplies Modules 2.1(Shunt Voltage Regulators) and 2.2 (Series Voltage Regulators). Below the reverse breakdown voltage, although only a small reverse leakage current is flowing, some current does flow and therefore electrons and holes are entering the depletion layer. The electrons present in the depletion region utilize that energy and get separated with the parent atom. During its movement, minority carriers collide with the atoms and generate more number of free electrons. The zener diode's operation depends on the heavy doping of its p-n junction. This voltage is known as zener voltage. This diode operates in zener breakdown or avalanche breakdown, However the word zener is used for all components having sharp breakdown characteristics in reverse direction. In this article, let us learn the function of Zener diodes along with its construction, operation and more. Both the zener and avalanche effects are also dependant to some degree on the junction temperature of the diode. Avalanche breakdown is usually subjected to happen when the applied reverse bias voltage is high. The wire is either slicked mechanically or electricaly. The actual breakdown voltage is controlled during manufacture by adjusting the amount of doping used. Most of the diodes are made from silicon because it can afford high temperature, however, germanium is also used for manufacturing where low voltage drop is required. In reverse biased condition, a small reverse current flows due to minority charge carriers. When Zener diodes are biased in their forward direction, with the anode voltage higher than the cathode, they behave in the same way as a normal silicon diode. All rights reserved. 0. But an avalanche diode carefully manufactured to operate in breakdown region withstand the high current flowing through it. However, whist the current in a purely zener diode has a negative temperature coefficient i.e. Zener impedance: Zener impedance is basically termed as the dynamic resistance of the zener diode. The zener diode is fabricated from the element silicon (Si). This high current is responsible for the permanent destruction of a normal diode. Let us separately understand the two breakdown mechanism. Thus, is used in the construction of zener diode. The layer of SiO2 helps to prevent contamination of the junctions. Zener diodes are a modified form of PN silicon diode used extensively for voltage regulation. The limiting (maximum) power for a zener diode is given by P z=V zI zmax and is a function of the design and construction of the diode. Construction of a voltage regulator is easy with the help of an ideal Zener diode, merely connecting the diode between the unregulated source of voltage and ground. The area of point contact diode is very small. This needs … special type of diode that lies at the heart of voltage regulators and circuits generating the reference voltage for a differential amplifier The heavily doped p + layer act as an anode. The current through the device is limited by making use of external resistance. This process is called ‘Avalanche Breakdown’. The P type and N type silicon used is doped more heavily than a standard PN diode. The Zener diode's operation depends on the heavy doping of its p-n junction. The construction of vacuum tubes is a bit complex and they are difficult to maintain when compared with the semiconductor diodes. 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