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Diodes in "series" is safe and ok?


What is (is or are ? ) electrical characteristics of series diodes? like 2 diode with 100V reverse voltage and 1A forward current ?

Nigel Goodwin

Super Moderator
Most Helpful Member
As with paralleled diodes you should balance them - in this case with high value resistors in parallel with each diode - otherwise they won't share equally, and one diode (and then both) WILL fail. Spec wise, current same, voltage double.


Here you can see two non matched diodes and the effects -

1) They have unbalanced power dissipation.
2) In reverse conduction one takes a lot more Vreverse than the other.
3) In forward conduction they have substantially different Vforward drop.

A way or partially equalizing the differences is to start a R in parallel with each
diode. But that leads to higher Ireverse going thru the load which may or may not
be a problem. So you trade off equalization with I reverse, but improve the balance
of Vreverse that the diodes experience.


Note in this example I did not use two of the same diode, so example might be more
extreme, but even using 2 of the same diodes, because of the log Vforward, one might
experience a lot more Pdissipation in one of the diodes, so that would have to be examined.

With 1K's strapped across each diode the Vreverse is much better balanced -


Regards, Dana.
Last edited:

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