/sci/ - Science & Math » Thread #13716708

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brainlet eng grad here

Anonymous Tue 05 Oct 02:47:37 2021 No.13716708 View Reply Original Report

Quoted By: >>13716833 >>13718242 >>13718325 >>13718760

pic related is the current equation on a diode, as the temperature increase it is well know that the current (I) for a given tension (Vd) increases, but if i increase the temperature (Vt) the value of (e^(Vd/Vt) drecreases, where is my brain not working here?

Anonymous

Anonymous Tue 05 Oct 2021 03:48:48 No.13716833 Report

Quoted By: >>13718208

>>13716708
what's the problem with the current tending to it's saturation value as temperature increases?

Anonymous

Anonymous Tue 05 Oct 2021 04:16:25 No.13716887 Report

Quoted By: >>13718208

I wish english used tension instead of voltage, it's a lot more intuitive

but you're forgetting that in real circuits, the current and voltage are not in terms of each other, but in terms of power

the maximum current and maximum voltage are limited by the total power of the circuit, which remains constant (presumably)

as the voltage goes lower, the current must get higher, since P=VI=constant, and if it's to remain constant, V and I gotta balance out

Anonymous

Anonymous Tue 05 Oct 2021 13:57:32 No.13718208 Report

Quoted By: >>13718242

>>13716833
how do you get that I is the saturation current?

>>13716887
got it, thanks

i wish the fucking books would have a note about this, its not obvius

Anonymous

Anonymous Tue 05 Oct 2021 14:04:31 No.13718242 Report

Quoted By:

>>13716708
your brain is working. Think of it this way : Heat fucks with electronics.

Try to draw the exponent for different values of temp. You'll notice that the exponent gets flatter and flatter as temp goes. And that's what sucks. Good diodes have a steep characteristic, meaning that it either lets all current in at an exact value, or lets none of it go.

If the exponent term isn't steep enough, say because the diode is getting too hot, then that means that at a voltage where you think the diode is on, it's only partly on.

>>13718208
if VT goes to infinity, the exponent is nullified, therefore I= -Is

Anonymous

Anonymous Tue 05 Oct 2021 14:22:39 No.13718325 Report

Quoted By: >>13721201

>>13716708
$V_T$ is not temperature

Anonymous

Anonymous Tue 05 Oct 2021 16:14:21 No.13718760 Report

Quoted By:

>>13716708
Is is also a function of the temperation and overcompensating the loss from Vt

Anonymous

Anonymous Wed 06 Oct 2021 06:58:39 No.13721201 Report

Quoted By:

>>13718325
It is proportional though

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