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AMS Semiconductor Tutorials

Tutorials Graphic We provide tutorials to help our customers better understand semiconductors and other electronic devices. Whether you have a question regarding a particular component, or simply want to know more about semiconductors, browse through our tutorial section for help. If you are still stuck, give us a call at (973) 377-9566 and we'll be happy to recommend a device for your application.

« Unijunctio... | Varactor diode | Zener Diode »
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Varactor diode Tutorial

     The varactor diode symbol is shown below with a diagram representation.

5A.jpg (4781 bytes)     5B.jpg (5708 bytes)

     When a reverse voltage is applid to a PN junction , the holes in the p-region are attracted to the anode terminal and electrons in the n-region are attracted to the cathode terminal creating a region where there is little current.This region ,the depletion region, is essentially devoid of carriers and behaves as the dielectric of a capacitor.

     The depletion region increases as reverse voltage across it increases; and since capacitance varies inversely as dielectic thickness, the junction capacitance will decrease as the voltage across the PN junction increases. So by varying the reverse voltage across a PN junction the junction capacitance can be varied .This is shown in the typical varactor voltage-capacitance curve below.

5C.jpg (27948 bytes)

     Notice the nonlinear increase in capacitance as the reverse voltage is decreased. This nonlinearity allows the varactor to be used also as a harmonic generator.

Major varactor considerations are:
(a) Capacitance value
(b) Voltage
(c) Variation in capacitance with voltage.
(d) Maximum working voltage
(e) Leakage current

« Unijunctio... | Varactor diode | Zener Diode »
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