DIODO VARACTOR PDF

Varactor Diodes are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for Varactor Diodes. Modulación con diodo varactor. La figura muestra el diagrama de un generador más práctico de FM que usa un diodo varactor, para desviar la frecuencia. [a] Il diodo Varactor a giunzione lineare In particular, the diode In has a CT of- 1 pF La capacità di transizione è tanto maggiore quanto – 1 pF.

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In electronicsa varicap diodevaractor diodevariable capacitance diodevariable reactance diode or tuning diode is a type of diode designed to exploit the voltage-dependent capacitance of a reverse-biased p—n junction. Varactors are used as voltage-controlled capacitors. They are commonly used in voltage-controlled oscillatorsparametric amplifiersand frequency multipliers.

Phase-locked loops are used for the frequency synthesizers that tune many radios, television setsand cellular telephones. The varicap was developed by the Pacific Semiconductor subsidiary of the Ramo Wooldridge Corporation who received a patent for the device in June This helps explain the different names for the device as it came into use.

Varactors are operated in a reverse-biased state, so no DC current flows through the device. The amount of reverse bias controls the thickness of the depletion zone and therefore the varactor’s junction capacitance. Generally, the depletion region thickness is proportional to the square root of the applied voltage, and capacitance is inversely proportional to the depletion region thickness. Thus, the capacitance is inversely proportional to the square root of applied voltage.

All diodes exhibit this variable junction capacitance, but varactors are manufactured to exploit the effect and increase the capacitance variation. The figure shows an example of a cross section of a varactor with the depletion layer formed of a p—n junction.

This depletion layer can also be made of a MOS or a Schottky diode.

Generally the use of a varicap diode in a circuit requires connecting it to a tuned circuitusually in parallel with any existing capacitance or inductance. The DC bias voltage must be blocked from entering the tuned circuit. Sometimes, with very high-Q tuned circuits, an inductor is placed in series with the resistor to increase the source impedance of the control voltage so as not to load the tuned circuit and decrease its Q.

Another common configuration uses two back-to-back anode to anode varicap diodes. See lower left circuit in diagram.

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Advanced Semiconductor

The second varicap effectively replaces the blocking capacitor in the first circuit. This reduces the overall capacitance and the capacitance range by half, but has the advantage of reducing the AC component of voltage across each device and has symmetrical distortion should the AC component possess enough amplitude to bias the varicaps into forward conduction.

A third circuit, at dkodo right in diagram, ciodo two series-connected varicaps and separate DC and AC signal ground connections. The DC ground is shown as a traditional ground symbol, and the AC ground as an open triangle.

NXP BBY40,215 Varactor, 26pF min, 5:1 Tuning Ratio, 30V, 3-Pin SOT-23 (TO-236AB)

Separation of grounds is caractor done to i prevent high-frequency radiation from the low-frequency ground node, and ii prevent DC currents in the AC ground node changing bias and operating points of active devices such as varicaps and transistors. These circuit configurations are quite common in television tuners and electronically tuned broadcast AM and FM receivers, as well as other communications equipment and industrial equipment.

Early varicap diodes usually required a reverse voltage range of 0—33 v to obtain their full capacitance ranges, which were still quite small, approximately 1—10 pF.

These types were — and still are — extensively used in television tuners, whose high carrier frequencies require only small changes in capacitance. Some designs of electronic security tag readers used in retail outlets require these high capacitance varicaps in their voltage-controlled oscillators. The three leaded devices depicted at the top of the page are generally two common cathode connected varicaps in a single package.

This is done to keep costs down — two dual packages could have been used, one for the tank and one for the oscillator, four diodes in all, and this is what was depicted in the application data for the LAN AM radio chip. Two lower-capacitance dual varactors used in the FM section which operates at a frequency about one hundred times greater are highlighted by red arrows. Special types of varicap diode exhibiting an abrupt change in capacitance can often be found in consumer equipment such as television tuners, which are used to switch radio frequency signal paths.

When in the high capacitance state, usually with low or no bias, they present a low impedance path to RF, whereas when reverse biased their capacitance abruptly decreases and their RF impedance increases. Although they are still slightly conductive to the RF path, the attenuation they introduce decreases the unwanted signal to an acceptably low level. They are often used in pairs to switch between two different RF sources such as the VHF and UHF bands in a television tuner by supplying them with complementary bias voltages.

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In some applications, such as harmonic multiplicationa large signal amplitude alternating voltage is applied across a varicap to deliberately vary the capacitance at signal rate to generate higher harmonics, which are extracted through filtering.

If a sine wave current of sufficient amplitude is applied driven through a varicap, the resultant voltage gets “peaked” into a more triangular shape, and odd harmonics are generated. All semiconductor junction devices exhibit the effect, so they can be used as varicaps, but their characteristics will not be controlled and can vary widely between batches.

Advanced Semiconductor – datasheet pdf

Popular makeshift varicaps include LEDs, [5] 1NX series rectifier diodes, [6] Schottky rectifiers and various transistors used with their collector-base junctions reverse biased, [7] particularly dioxo 2N and BC Maximum reverse bias voltage is usually between 5 and 7 Volts, before the avalanche process starts conducting.

Higher-current devices with greater junction area tend to possess higher capacitance.

From Wikipedia, the free encyclopedia. Varicap diode Internal structure of a varicap.

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Microelectronic circuits 6th ed. Dr Tuttle’s Home Page. Retrieved 23 January Mann, “Voltage sensitive semiconductor capacitor”, published 23 Mayissued 20 Juneassigned to Pacific Semiconductors, Inc.

The Art of Linear Electronics. Potentiometer digital Variable capacitor Varicap. Capacitor types Ceramic resonator Crystal oscillator Inductor Parametron Relay reed relay mercury switch. Retrieved from ” https: Wikipedia articles needing clarification from May Articles needing additional references from September All articles needing additional references Wikipedia articles needing clarification from January Commons category link is on Wikidata Wikipedia articles with GND identifiers.

Views Read Edit View history. In other projects Wikimedia Commons. This page was last edited on 12 Novemberat By using this site, you agree to the Terms of Use and Privacy Policy. Internal structure of a varicap. Wikimedia Commons has media related to Varicaps.