Stocking up on mosfets

[birdman0_o]

Hey guys,

I'm thinking of stocking up on mosfets sometime soon and I was just wondering if there is such thing as "overqualified" mosfets, in other words: Would it be wise to buy ~100 amp mosfets to use on any project? I don't see why there would be a problem, maybe just that they cost a bit more, perhaps they would be better suited because of the lower RDS?

Let me know what you think

Mike

 

[Hero999]

Gernally the higher the power the better but higher specs do cost more.

Another thing to be aware of is that larger MOSFETs often have a higher gate capacitance and the maximum gate voltage on some low threashold high current types is quite low - I've seen some as low as 10V.

 

[dknguyen]

Other than cost, larger MOSFETs might have a lower RDson, but they also turn on slower (for a given drive current) increasing switching losses. Depending on what you are doing, they might run a lot hotter than you expect if you do not use sufficient drive even with a lower RDson because the RDson losses become negligible, but become dominated by the switching loss.

 

[Sceadwian]

By my way of thinking it seems best to buy three types. Small signal monolithics, medium power, and high power, with 25% going to P type and the rest N type. You'll want the small signal fets to be logic level, and maybe 25% of the power fets to be logic level. Not very common but depletion mode power fets have a place as well. Granted that's a lot of different types of fets, but you should cover your bases. Depends highly on what you think you'll be using the FET's for. I just covered what I think would be a general spread.

 

[unclejed613]

if you're thinking of doing any audio stuff, you might consider getting lateral Mosfets, but beware of fakes. it seems lateral MOSFETS are high on the counterfeiting hit list because demand is high. same goes for the other MOSFETS as well. use suppliers like Digi-Key (i've seen their ads on this forum) or B&D, MCM, or Mouser. i know B&D has genuine laterals because i have bought them for an amp repair. 2SK1058/2SJ162 are excellent devices for audio amps.