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Ligne 75 :
Ligne 75 : − + − Just like any component, diodes can only dissipate so much power before they blow. All diodes should list maximum current, reverse voltage, and power dissipation. If a diode is subject to more voltage or current than it can handle, expect it to heat up (or worse; melt, smoke,…).+ − Some diodes are well-suited to high currents – 1A or more – others like the 1N4148 small-signal diode shown above may only be suited for around 200mA.+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
→Fiche technique d'une Diode
[[Fichier:Diode-fiche-technique-1N4148-02.png]]
[[Fichier:Diode-fiche-technique-1N4148-02.png]]
Ce graphique met en évidence une autre caractéristique importante des diodes – le courant maximal dans le sens passant ("''maximum forward current''" aussi noté If(max) ).
'''Ce graphique met en évidence une autre caractéristique importante''' des diodes – le courant maximal dans le sens passant ("''maximum forward current''" aussi noté If(max) ).
Comme tous les autres composants, les diodes sont capable de dissiper une quantité d'énergie maximale avant de claquer.
Toutes les diodes devraient lister les caractéristiques:
* maximum current - courant maximum,
* reverse voltage - tension inverse,
* power dissipation - puissance dissipée.
Si une diode se voit appliquer une tension (ou un courant) plus important que ce qu'elle peut supporter alors attendez vous à la voir chauffer (ou pire; fondre, fumer, exploser, ...).
Certaines diodes sont conçues pour des courants importants – 1A ou plus – d'autres diodes comme la 1N4148 est une diode "''small-signal''" et plutôt destinée à un courant d'environ 200mA.
= Les types de Diodes =
== Les diodes normales ==
Standard '''signal diodes''' are among the most basic, average, no-frills members of the diode family. They usually have a medium-high forward voltage drop and a low maximum current rating. A common example of a signal diode is the 1N4148. Very general purpose, it’s got a typical forward voltage drop of 0.72V and a 300mA maximum forward current rating.
[[Fichier:Diode-1N4148.png]]<small><br />A small-signal diode, the 1N4148. Notice the black circle around the diode, that marks which of the terminals is the cathode.</small>
A '''rectifier or power diode''' is a standard diode with a much higher maximum current rating. This higher current rating usually comes at the cost of a larger forward voltage. The 1N4001, for example, has a current rating of 1A and a forward voltage of 1.1V.
[[Fichier:Diode-1N4001.png]]<small><br />A 1N4001 PTH diode. This time a gray band indicates which pin is the cathode.</small>
And, of course, most diode types come in surface-mount varieties as well. You’ll notice that every diode has some way (no matter how tiny or hard to see) to indicate which of the two pins is the cathode.
[[Fichier:Diode-CMS.jpg]]
== Diodes émettant de la lumière ==
The flashiest member of the diode family must be the light-emitting diode (LED). These diodes quite literally light up when a positive voltage is applied.
[[Fichier:Diode-LED.jpg]]
Like normal diodes, LEDs only allow current through one direction. They also have a forward voltage rating, which is the voltage required for them to light up. The VF rating of an LED is usually larger than that of a normal diode (1.2~3V), and it depends on the color the LED emits. For example, the rated forward voltage of a Super Bright Blue LED is around 3.3V, while that of the equal size Super Bright Red LED is only 2.2V.
You’ll obviously most-often find LEDs in lighting applications. They’re blinky and fun! But more than that, their high-efficiency has lead to widespread use in street lights, displays, backlighting, and much more. Other LEDs emit a light that is not visible to the human eye, like infrared LEDs, which are the backbone of most remote controls. Another common use of LEDs is in optically isolating a dangerous high-voltage system from a lower-voltage circuit. Opto-isolators pair an infrared LED with a photosensor, which allows current to flow when it detects light from the LED. Below is an example circuit of an opto-isolator. Note how the schematic symbol for the diode varies from the normal diode. LED symbols add a couple arrows extending out from the symbol.
[[Fichier:Diode-OPTO.jpg]]
== Diodes Schottky ==
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