[sdiy] how to double Si diode voltage rating

[Roy J. Tellason]

On Tuesday 26 February 2008 00:31, KA4HJH wrote:
> >If I wanted to increase current carrying capability would I put the diodes
> >in parallel? Like if I wanted to use 1N4007's (since I have a ton) and I
> >needed 2Amps?
>
> Back when I was learning electronics they told me that unless you've got
> them matched really well you NEVER put diodes in parallel, especially
> rectifiers. One of them will get more current than the other(s) and be the
> first to fail.
>
> These days I see it done all the time, mainly with LED's. Perhaps something
> has changed while I wasn't looking?

With LEDs there's some other factor limiting the current,  typically an 
external resistor (though I have run across some that appeared to have 
internal current-limiting,  they'd run just fine on 5-12VDC with little 
change in brightness,  but that's another story).

With rectifiers,  one will take more current than the other,  unless you put 
something in there to even things out.  And the hotter one will have a lower 
voltage drop since a forward-biased junction has that kind of a temperature 
coefficient,  which means that it'll tend to hog more of the current,  and so 
forth,  until something fails.

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