Varicap


Varicap

In electronics, a varicap diode, varactor diode, variable capacitance diode or tuning diode is a type of diode which has a variable capacitance that is a function of the voltage impressed on its terminals.

Applications

Varactors are principally used as a voltage-controlled capacitor, rather than as rectifiers. They are commonly used in parametric amplifiers, parametric oscillators and voltage-controlled oscillators as part of phase-locked loops and frequency synthesizers.

Operation

Varactors are operated reverse-biased so no current flows, but since the thickness of the depletion zone varies with the applied bias voltage, the capacitance of the diode can be made to vary. 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 phenomenon to some degree, but specially made varactor diodes exploit the effect to boost the capacitance and variability range achieved - most diode fabrication attempts to achieve the opposite.

External links

* [http://www.vias.org/simulations/simusoft_varactor.html Learning by Simulations] Calculation of the characteristics of a varactor diode for various doping profiles
* [http://www.maxim-ic.com/appnotes.cfm/an_pk/2032] Trimless IF VCO: Part 1: Design Considerations from Maxim.

Further reading

* Mortenson, Kenneth E. (1974). "Variable capacitance diodes: the operation and characterization of varactor, charge storage and PIN diodes for RF and microwave applications". Dedham, Mass.: Artech House.
* Penfield, Paul and Rafuse, Robert P. (1962). "Varactor applications." Cambridge, M.I.T. Press.


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  • varicap — VARICÁP, varicape, s.n. (electron.) Varactor. – Din fr. varicap. Trimis de bogdanrsb, 13.09.2007. Sursa: DEX 98  VARICÁP s. (FIZ.) varactor. Trimis de siveco, 05.08.2004. Sursa: Sinonime  varicáp s. m., pl. varicápe …   Dicționar Român

  • varicap — [vaʀikap] n. f. ÉTYM. 1968; mot angl. des États Unis, de vari(able) cap(acitor) « condensateur variable ». ❖ ♦ Techn. Électron. Diode semi conductrice dont la capacité varie suivant la pression appliquée …   Encyclopédie Universelle

  • Varicap —   [ værɪkæp], Akronym aus englisch variable capacitor, Varaktor …   Universal-Lexikon

  • varicap — varikapas statusas T sritis fizika atitikmenys: angl. varactor; variable capacitance diode; varicap vok. Varaktor, m; Varikap, n rus. варактор, m; варикап, m pranc. diode à capacité variable, m; varacteur, m; varicap, m …   Fizikos terminų žodynas

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  • Diode Varicap — La diode à capacité variable ou varicap est une sorte de diode utilisée comme condensateur variable. Représentation symbolique d une diode varicap Fonctionnement Lors de son utilisation, la diode varicap (terme qui est une abréviation de l… …   Wikipédia en Français

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