EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: micnolmad on February 24, 2016, 12:38:47 pm
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Diodes are hard! A resistor is easy, there are many apps and articles on how to use them and so.
As a newcomer to diodes I am struggling to find a good way to find the right diode for the job. By find I mean some sort of tool, app or db with some search parameters to narrow it down. I do understand the math the various elements of a diode once I know what the characteristics it should have how do proceed? There must be some form of lookup tool?
Thanks
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Look at supplier sites such as Digikey. Diodes can be filtered to your specifications as they give you a lot of choices and allow you to choose the characteristics which fit your needs.
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You can pretty much get by on a half dozen diodes. That said there is a reason for each diode. Things are complicated further when some diodes don't exactly match their specifications. Forward voltage really irks me when I see it mentioned in posts as .25V and .6V and in actual applications it is nowhere near that.
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A 1N4148 general purpose silicon diode is 0.6V at a current of about 700uA. Its maximum allowed reverse voltage is 75V and its maximum allowed continuous current is 300mA.
A 1N5817 Schottky diode is 0.25V at a current of about 20mA. Its max allowed reverse voltage is 20V and its maximum allowed average rectified current is 1A.
The above diodes switch very quickly.
A 1N4001 rectifier has a maximum allowed reverse voltage of 50V and a max allowed average rectified current of 1A but its max allowed momentary current is 30A! It switches very slowly so is used only for DC or for 50Hz and 60Hz mains rectifying.
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all kind of them need be know :)
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I use a SB5100 5.0A 100V SCHOTTKY diode generic and cheap. Spec say .52V forward at 1A in real life about .665 and it gets worse with more current. Once you get over 50V there isn't much advantage other than speed.
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Thank you all for participating.. Adam 60, ty. Clear and useful answer.
The rest of the posts felt more like a private discussion then an answer to the OP or am I just not getting the meaning?