# derating of MOSFET

I am trying to study a MOSFET for a space application. One of the things I have to do is study the derating analysis for a MOSFET. I am refering the document obtained from ESA site - ESA site link.

I am also attaching a screen shot below that has the derating parameter info. The parameters are Vgs,Vds,Ids,...etc.

I understand the parameters. But what do I derate it with ? The MOSFET under consideration- Mosfet under consideration Let me explain my understanding - My desired/required Vds - 5V. The Vds of the said MOSFET is 60V. Now, 80% of that is 48V. So, this one is apt. Supposing, I selected a MOSFET with Vds of 5, then after the 80% rule application the value is 4. This other MOSFET is not apt.

Is my analysis correct ?

Also, the last page of the datasheet shows the SEE curve.

How do I analyse that ? Why is the gate bias negative? It is an N Channel MOSFET.

In page 1 there are 2 specifications viz - ABSOLUTE MAXIMUM RATINGS and PRE-IRRADIATION ELECTRICAL CHARACTERISTICS. Whats is the value I should be looking at? And what is the difference between the 2 please ?

Finally, it states - Note: (1) Derated Linearly by 1.2 W/°C for TC > +25°C. Also, is the 150W valid at 25degree celcius ? How, do I decipher that ? For eg at 50degrees Celcius ?

What I understand is that the slope of the derating(wattage) is 1.2. This implies that 1.2 =(150-x)/(25-50). Hence x = 180????? Thats not possible.