does this IGBT have a negative or positive temp coefficient?

[strantor]

https://www.electro-tech-online.com/custompdfs/2011/09/cm1200ha-24j_dat.pdf
I can't seem to find the answer in the datasheet. I also don't see a temperature vs. current graph. How can I tell by looking at a datasheet if an IGBT has a negative or positive temp coefficient?
thanks

 

[Grossel]

Very good question. Different sources on the web tells different.

 

[BrownOut]

Look closely at the output characterics graph for IC vs VGE. It has curves for tj=25 degrees C and tj=125 degrees C. Looks slightly positive to me.

 

[strantor]

Look closely at the output characterics graph for IC vs VGE. It has curves for tj=25 degrees C and tj=125 degrees C. Looks slightly positive to me.

Ok, looking at that graph, what I see is that the hotter it gets, the less voltage it takes at the gate to get the same amps out, which to me says negative temp coefficient. I'm not sure my logic is right though. I thought the temperatur coefficient had to do with the resistance between collector and emitter and temperature. negative temp coefficient would mean that as it gets hotter, the resistance goes down, which makes it hotter, so resistance goes down further, etc. thermal runaway. can we associate VGE with RCE?

 

[BrownOut]

The hotter it gets, the more output current for the same gate voltage. Read the graph vertically. A positive current/temperature coefficient means more current over temperature.

We generally talk about transconductance of a transistor, rather than resistance between the collector and emitter, since transconductance is an active parameter.

 

[strantor]

what I see is that the hotter it gets, the less voltage it takes at the gate to get the same amps out

The hotter it gets, the more output current for the same gate voltage. Read the graph vertically.

I think we are saying the same thing in a different way. 6 of one, half dozen of another.

A positive current/temperature coefficient means more current over temperature.

We generally talk about transconductance of a transistor, rather than resistance between the collector and emitter, since transconductance is an active parameter.

Sorry, I'm not very familiar with IGBTs. I have spent the last week researching MOSFETS where they always specify Rdson, so that is how I was thinking of the junction between Collector & emitter of IGBT. So I'm (a little dense) still not sure whether you are saying this IGBT is prone to thermal runaway or not.

 

[BrownOut]

I think we are saying the same thing in a different way.

Yes. But if you think of it as an increase in output current rather than a decrease in gate voltage, then the positive relationship between temp and current is easier to see.

still not sure whether you are saying this IGBT is prone to thermal runaway or not.

It is.

 

[strantor]

Thank you very much my friend