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Diodes - Surface Mounted

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1 Diodes - Surface Mounted on Wed Dec 04, 2013 10:31 am

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In [You must be registered and logged in to see this link.], a diode is a two-[You must be registered and logged in to see this link.] [You must be registered and logged in to see this link.] that conducts [You must be registered and logged in to see this link.] in only one direction. The term usually refers to a semiconductor diode, the most common type today, which is a crystal of [You must be registered and logged in to see this link.] connected to two electrical terminals, a [You must be registered and logged in to see this link.]. A vacuum tube diode, now little used, is a [You must be registered and logged in to see this link.] with two [You must be registered and logged in to see this link.]; a [You must be registered and logged in to see this link.] and a [You must be registered and logged in to see this link.].
The most common function of a diode is to allow an electric current in one direction (called the diode's forward direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a [You must be registered and logged in to see this link.]. This unidirectional behavior is called [You must be registered and logged in to see this link.], and is used to convert [You must be registered and logged in to see this link.] to [You must be registered and logged in to see this link.], and extract [You must be registered and logged in to see this link.] from radio signals in radio receivers.
However, diodes can have more complicated behavior than this simple on-off action, due to their complex [You must be registered and logged in to see this link.] electrical characteristics, which can be tailored by varying the construction of their [You must be registered and logged in to see this link.]. These are exploited in special purpose diodes that perform many different functions. Diodes are used to regulate voltage ([You must be registered and logged in to see this link.]), electronically tune radio and TV receivers ([You must be registered and logged in to see this link.]), generate [You must be registered and logged in to see this link.] [You must be registered and logged in to see this link.] ([You must be registered and logged in to see this link.]), and produce light ([You must be registered and logged in to see this link.]).
Diodes were the first [You must be registered and logged in to see this link.]. The discovery of crystals' [You must be registered and logged in to see this link.] abilities was made by German physicist [You must be registered and logged in to see this link.] in 1874. The first semiconductor diodes, called [You must be registered and logged in to see this link.] were made of crystals of minerals such as [You must be registered and logged in to see this link.]. Today most diodes are made of [You must be registered and logged in to see this link.], but other [You must be registered and logged in to see this link.] such as [You must be registered and logged in to see this link.] are sometimes used.

Types of semiconductor diode in Mobile Phones Circuit

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Diodes that can be made to conduct backwards. This effect, called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. In practical voltage reference circuits Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient to near zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes (see above). Two (equivalent) Zeners in series and in reverse order, in the same package, constitute a transient absorber (or [You must be registered and logged in to see this link.]Transorb, a registered trademark). The Zener diode is named for Dr. [You must be registered and logged in to see this link.]Clarence Melvin Zener of Southern Illinois University, inventor of the device.
[You must be registered and logged in to see this link.] (LEDs)
In a diode formed from a [You must be registered and logged in to see this link.]direct band-gap semiconductor, such as [You must be registered and logged in to see this link.]gallium arsenide, carriers that cross the junction emit [You must be registered and logged in to see this link.]photons when they recombine with the majority carrier on the other side. Depending on the material, [You must be registered and logged in to see this link.]wavelengths (or colors) from the [You must be registered and logged in to see this link.]infrared to the near [You must be registered and logged in to see this link.]ultraviolet may be produced. The forward potential of these diodes depends on the wavelength of the emitted photons: 1.2 V corresponds to red, 2.4 V to violet. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time. All LEDs produce incoherent, narrow-spectrum light; “white” LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow [You must be registered and logged in to see this link.]scintillator coating. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an [You must be registered and logged in to see this link.]opto-isolator.
   [You must be registered and logged in to see this link.]Photodiodes
All semiconductors are subject to optical [You must be registered and logged in to see this link.]charge carrier generation. This is typically an undesired effect, so most semiconductors are packaged in light blocking material. Photodiodes are intended to sense light([You must be registered and logged in to see this link.]photodetector), so they are packaged in materials that allow light to pass, and are usually PIN (the kind of diode most sensitive to light). A photodiode can be used in [You must be registered and logged in to see this link.]solar cells, in [You must be registered and logged in to see this link.]photometry, or in [You must be registered and logged in to see this link.]optical communications. Multiple photodiodes may be packaged in a single device, either as a linear array or as a two-dimensional array. These arrays should not be confused with [You must be registered and logged in to see this link.]charge-coupled devices.

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