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Common Cathode Diode Module


Jaco De Jongh
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I realized yesterday that the reason is other.

I was making a power circuit with some Mosfets in parallel and i thought about this post. We can install the mosfet we want in parallel because Mosfet are PTC. That means that power mosfet resistance increase with temperatura. Then if one mosfet brings more current than other, its resistance increases and its drain current decreases. Then all mosfet in parallel are balanced.

But, what happens whit PN discrete semiconductors? PN, diode, BJT, or IGBT, are NTC. That means their resistance decreases when temperature gets higher. That´s the reason why we can´t put diode in parallel. If one of them runs more current its temperature increases and its resistance decreases and it runs more and more current untill it destroys itself. 

The solution to use a pair of diodes in parallel is to be sure that they have the same temperature. How? Sharing the case, as we can see in your picture.

 

Edited by Javi Martínez
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