What to look when looking for a FET or MOSFET equivalent

[gkmaia]

What are the key ratings to consider when replacing a FET or MOSFET for and equivalent apart from voltage and current ratings?

[magic]

SOA, threshold voltage, RDS(on), gate charge, zillion of things...

What kind of application, what kind of FET?

[gkmaia]

I suspected you could look at a zillion things, but if you were to simplify these zillion things to a couple that are the most critical ones apart from voltage and current what would those be?

[Circlotron]

The most critical things vary, depending on the application. If you tell us the application we can narrow things down a *lot*.

[aheid]

You can simplify somewhat but it is highly dependent on application. Attributes which are important in some applications can lead to detrimental aspects for another application. For example a good switching MOSFET typically won't work well in the linear regime. IIRC high voltage tolerance leads to higher capacitance, which is very bad for other applications.

[GeorgeOfTheJungle]

The thing I always double check is Gate Threshold VGS_(TH)

[magic]

Probably mostly the things I listed before.

Load switching: RDS(on) and VGS(on)
PWM: ditto plus perhaps gate charge
Linear: SOA, power dissipation vs temperature, maybe VGS(th)