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What is the usual breakdown voltage for these cheap and common LEDs? For example are they able to operate between -9V and +9V states(on and off) for a long duration? Or does having -9V across these LEDs destroy them?

The current limiting resistor will be used by the way.

edit: while speaking about these LEDs, I refer to the ones you can or anyone can find in lots of examples, simple project tutorials on the internet etc. I have watched almost 100s of these videos, read tutorials but never seen anybody referring which LED model they are using. They just call it as "LED" and one can find it very easily. I refer those LEDs.

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    \$\begingroup\$ You need a datasheet for each part. The fact they're all packaged with a 3-mm blob of epoxy around them tells you almost nothing about the characteristics of the actual device. \$\endgroup\$
    – The Photon
    Commented Dec 12, 2019 at 17:54
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    \$\begingroup\$ Please provide a link to the datasheet for the LEDs. Without the datasheet no one can give you a definitive answer. \$\endgroup\$
    – Elliot Alderson
    Commented Dec 12, 2019 at 17:54
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    \$\begingroup\$ You've posted enough question on this site that it should have been apparent that only limited assumptions can be made when data for a particular part is not available, and that general advice here is not to buy undocumented parts when it is unclear if they will meet your needs. You can consider data sheets for possibly comparable products, but it would probably be better to make your design insensitive to this value by keeping reverse current out of the LED, either blocking it or giving it another path which will minimize the reverse voltage seen. \$\endgroup\$
    – Chris Stratton
    Commented Dec 12, 2019 at 18:06
  • \$\begingroup\$ @ChrisStratton see, you can answer this question by just saying "you cannot talk about a general reverse bd. voltage for LEDs." I never understood why some users on this site are this much offensive. I don't live in somewhere you can find all these nice manufacturers which will provide you with a datasheet even for a very cheap LED. In the boundaries of my possibilites, I can only buy those LEDs without having an information more than "this is LED". So, I asked that if there is some reasonable common value for this voltage or not. Thanks for the advice, anyway. \$\endgroup\$
    – muyustan
    Commented Dec 12, 2019 at 18:14

2 Answers 2

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All of these types of single discrete LEDs has a reverse voltage breakdown threshold of -5V. Never drive more than the absolute maximum specs in the datasheet and also expect > 50kh MTBF.

LITE-ON also add a note to every Absolute Maximum Rating Table : Reverse Voltage can't be continued operating

  • This also applies to forward current with a current limiting resistor.

  • Typically for Red, Yellow these are tested for -5V @ 1uA Max and for Blue, WHite, Green, -5V @10uA

    • This does not mean they will fail at -6V but that the current exponential rises at some point above -5V and the breakdown voltage and capacitance discharge will destroy the junction.
    • Even if one test worked at -9V you may conclude -9V is OK to use as there is an aging acceleration rate.
    • If they are all identical capacitance and leakage then it may be reasonable to assume if you had 20 in series that you could apply -100 V reverse and the ones which leak more then reduce in voltage drop to equalize.
  • By no coincidence this is also the same -5V reverse voltage rating for almost all NPN/PNP's as the heavily doped Vbe junctions in bipolar junction transistors has the same limitation, unlike the lighter doped Vbc diode which provides the high Vce voltage rating
    • (Vce = Vbc reverse + Vbe forward )

I see a difference in Anode gold wirebond in these packages due to the side of the flat D edge and the position of the reflective cup holder, but sometimes the transparent substrate is inverted. (caution)

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  • \$\begingroup\$ well thanks for the answer, but now I have to ask what does that ">50kh MTBF" mean? \$\endgroup\$
    – muyustan
    Commented Dec 12, 2019 at 18:26
  • \$\begingroup\$ If you can't google "MTBF" Your journey to master electronics will be slow. \$\endgroup\$
    – D.A.S.
    Commented Dec 12, 2019 at 18:28
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    \$\begingroup\$ Mean time between failures = is a measure of average life for any equipment or parts. LEDs initially were 50k hours or 50kh and now much higher due to process quality improvements. So exceeding any ABS MAX spec degrades lifetime . it may be slow or sudden \$\endgroup\$
    – D.A.S.
    Commented Dec 12, 2019 at 18:33
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    \$\begingroup\$ Perhaps I was not clear. IF you drive an LED in reverse , expect a shorter life. How much depends on uA current. which is rated at -5V... for NPN the PN base emitter reverse = -5V while the PN jcn. Vce = Vbc reverse + Vbe forward \$\endgroup\$
    – D.A.S.
    Commented Dec 12, 2019 at 18:38
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    \$\begingroup\$ the -5V is a property of physics for PN junctions when they are heaviliy doped junctions like LEDs. It is like a tiny weak Zener diode threshold that fails with low levels of power .. e.g. breakdown voltage of Vce can be used as a weak high voltage zener, but not recommended for Vbe or LED in reverse as the junction capacitance breakdown effects may be more destructive \$\endgroup\$
    – D.A.S.
    Commented Dec 12, 2019 at 18:45
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See the datasheet. The Cree C503B, for example specifies a reverse voltage of 5 V.

As I think you suspect, the limiting resistor only has any effect once current starts flowing. In reverse bias the full supply voltage appears across the diode junction.

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  • \$\begingroup\$ Yes I knew that, the thing that I don't know any of these LEDs model or part number so I could not find a datasheet. Thanks. This shows that I can do that operation(switching on and off) for -3/+3 volts but cannot do for -x/+x where x>5, right. \$\endgroup\$
    – muyustan
    Commented Dec 12, 2019 at 17:58
  • \$\begingroup\$ @muyustan What makes you think you can apply a forward voltage of 3V to these diodes? I'm not sure you understand how diodes work. \$\endgroup\$
    – Elliot Alderson
    Commented Dec 12, 2019 at 18:00
  • \$\begingroup\$ @ElliotAlderson aren't these LEDs generally have a 2.9-3.1 volts of forward bias voltage? \$\endgroup\$
    – muyustan
    Commented Dec 12, 2019 at 18:01
  • \$\begingroup\$ Are you trying to omit the series resistors? That's not usually a good idea. \$\endgroup\$
    – Transistor
    Commented Dec 12, 2019 at 18:05
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    \$\begingroup\$ I've never seen an LED with a reverse voltage specified as anything other than 5V, which might be worth noting. I imagine the reason has to do with the fact that they aren't intended to be used in reverse, and 5V is the most that might appear across them in reverse in 5V logic systems. \$\endgroup\$
    – Hearth
    Commented Dec 12, 2019 at 18:16

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