In microwave receiver LO, varactor diodes can be used as frequency multipliers. A varactor diode is specially constructed to have high capacitance under reverse bias, it varies its capacitance when it is applied reverse biased voltages. INTRODUCTION Varactor diode is a special type of PN junction diode, in which PN junction capacitance is controlled using reverse bias voltage. These diodes allow the filters to follow the frequency of the incoming received signal which can be restricted using a control voltage. A varactor diode, also called varicap, VVC (voltage-variable capacitance, or tuning diode, is a type of semiconductor diode which features a variable voltage-dependent capacitance on its p-n junction when the device is reversed biased. As varactors are often driven from a high impedance source, this limit is very acceptable. The space between them represents their dielectric. Variable Capacitance Characteristics. When the reverse bias voltage increases, the junction capacitance decreases, on the contrary, the junction capacitance increases. -It is a p-n junction with a special impurity profile, and its capacitance variation is very sensitive to reverse-biased voltage. Varactor diode doped with a very small quantity of impurities near the junction and impurity concentration increases moving away from the junction. Varactor Diode Characteristics The characteristics of varactor diodes are: The increase in reverse voltages increases the value of capacitance. See Figure 1 for a typical varactor voltage-capacitance characteristic. It is also known as varicap or voltcap. An important characteristic of any varactor diode is its Q. But unlike a zener diode they don’t allow the flow of current in zener breakdown regions. You can see that the symbol of this diode is alike to a normal diode. Characteristics and Parameters of Varactor Diode. They are voltage controlled capacitors and sometimes known as varicap diodes, although the word varactor is widely used. Cd diode capacitance VR =3V; f=1MHz; seeFgis2and4 26 32 pF VR = 25 V; f = 1 MHz; see Figs 2 and 4 4.3 6pF C capacitance ratio f = 1 MHz 5 6.5 d3V Cd25V ----- - 1996 May 03 3 NXP Semiconductors Product specification VHF variable capacitance diode BBY40 GRAPHICAL DATA Fig.2 Diode capacitance as a function of reverse voltage; typical values. Therefore, it is similar to the capacitor shown above. The varactor diodes are small in size and hence, they are very lightweight. Varactor diodes produce considerably less noise compared to other conventional diodes. 3. Varactor diode operates only in reverse bias. A diode is used for conversion of AC into DC, for this conversion rectifier circuits are used that uses diode. Varactor diode in tunning Circuit. 2. They are manufactured with gallium arsenide. A varactor is a diode that always operates in reverse bias and is doped to maximize the inherent capacitance of the depletion region. Varactor Diodes, also known as "variable reactance diodes", are made using the characteristic that the junction capacitance varies with the applied voltage when the PN junction is reverse biased. When the reverse bias increases, the width of the depletion region also increases resulting in less capacitance. Varactor diode is a semi-conductor device in which the junction capacitance can be varied as a function of the reverse bias of the diode. Characteristics of GaAs varactor diode. One end is an anode and the second has 2 lines that represent the plates of a capacitor. Varactor Diode. The depletion area between the P-type & N-type regions can be considered as the insulating dielectric. And to ensure that this diode is not influenced by the bias voltage in the circuit. term varactor is originated from a variable capacitor. They are voltage controlled capacitors and sometimes known as varicap diodes, although the word varactor is widely used. The varactor diode is small in size and less in weight. As a result these diodes are also referred to as varicaps, tuning diodes, voltage variable capacitor diodes, parametric diodes and variable capacitor diodes. Characteristics Of Varactor Diode: The typical curvature of the Varactor Diode is shown in the figure below. Varactor diodes are specifically fabricated and optimized such that they permit a high range of changes in capacitance. It can be seen in the characteristic curve that as reverse voltage increase from 0 V the transition capacitance is decreasing exponentially. Varactor diode 1. The relation between the transition capacitance, V R and V k . The V-I characteristics of the diode are non-linear and it permits the flow of current in only one direction In forward bias mode, the diode allows the flow of current and offers very low resistance. An important characteristic of any varactor diode is its Q. By using voltage control technique in the diode circuit, changing capacitance can be offered. Basics of varactor diode with design tips This page was last edited on 23 December 2020, at 00:45 (UTC). A The symbol of varactor diode is also shown in the resultant figure. Varactor diode 1. Title: Varactor Diode 1 Varactor Diode REPORT BY JOHN PAOLO LABARO 2 VARACTOR DIODE-Also known as Varicap Diode-Is a device whose reactance can be varied in a controlled manner with a bias voltage. Characteristics Of a Varactor Diode. Varactor diodes are used to vary the capacitance in variable resonant tank LC circuits. In today’s tutorial, we will have a look at Introduction to Varactor Diode. Varactor diodes are also referred to as varicaps or tuning diodes. Diodes are usually manufactured with complex technologies such as multiple diffusion or multiple implantation. - Structure & Tuning Methods. The Varactor diodes belong to the family of semiconductor devices. Varactor diode is also sometimes referred to as varicap diode, tuning diode, variable reactance diode, or variable capacitance diode. We already know we can find the capacitance using the following equation. o The Depletion region act as a capacitor di-electric because of its non conductive characteristic. The different types of Varactor diodes are available in the market such as hyper abrupt, abrupt and gallium-arsenide Varactor diodes. A few of the main applications of Varactor diodes can be listed below: Do you know any other diodes that are regularly used in real-time electrical and electronics projects Then, please give your feedback by commenting in the comments section below. These diodes are very small in size and very lightweight. The depletion region at the pn junction acts as the dielectric and plates of a common capacitor and is caused to expand and contract by the voltage applied to the diode. 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