Mosfet Selection....

[Fish4Fun]

Just read a response KrisBlueNZ made to a thread on a motor speed controller where he recommended a NTD4906 mosfet as a good choice for a low-voltage//low gate threshold switch.....

First, Great Catch! Sepcs on that little mosfet are fabulous and they are virtually free!

But that isn't really my point with this post (though I will certainly add some NTD4906s to my next digi-key order!)....My point with this post is that I am constantly searching for "lower cost"//"lower Tr/Tf"//"Lower RDSon"//"Lower Vgs" mosfets for whatever project I am playing with @ the time and I would like to think I am pretty good @ ferreting them out and then.... "Out of the 'Blue'" comes this NTD4906....OBVIOUSLY somebody other than Kris knew about this little gem of a mosfet, digi-key has nearly 80k IN STOCK....

So, perhaps there is some "secret" way of ferreting out mosfets that I am not privy to? A trick I frequently employ after narrowing some of the broader search parameters in digi-key's paramtric search engine is to sort by "quantity available"....the rationale being that what digi-key has the highest stock level in is frequently equivalent to their "best sellers", and there is generally a reason a particular part is a "best seller"....but this approach would NEVER have placed the above mosfet in the first 10 pages....so there MUST be some other tricks.....

Please Share any tips & tricks you might use to help find a particular mosfet for a particular application....inquiring minds REALLY want to know!

Fish

 

[KrisBlueNZ]

I just found the NTD4906 using the Digi-Key parametric search. I knew I wanted a through-hole part rated for at least a few amps. Then I sorted by price ascending, and went down the R_DS(on) column looking for decreasing numbers. Every time I found a number that was less than the lowest number I had found previously, that was a potentially cost-effective device. The NTD4906 just jumped out at me because it was a big jump in R_DS for a small increment in price. Once I found that one, I stopped looking!

It's only rated for 30V though, which limits its usefulness sometimes, but it's very cheap and compact and the specs are pretty amazing. Even at 5V V_GS it's around 8~9 mΩ I think.

 

[Fish4Fun]

Again, Great Catch! But, RDSon is only one spec that makes this particular mosfet really appealing for Low Voltage applications...the extremely low Vgs, Excellent Tf, and very good Tr all combined with exceptional value make me want to find a project for it! But I am a bit sad that you didn't reveal some "magic" way of ferreting out other exceptional mosfets.....I guess it all comes down to properly "narrowing the field" and then sorting by **something** and then start downloading PDFs .... reading ...... and stopping when you find something that meets all of the requirements....or your eyes start to bleed....I was just **HOPING** for an "Easy Button"....hehehe....

If anyone else has any "tips & tricks" PLEASE share them....or if anyone has come across a particularly great mosfet that "Stands Out" for any combination of reasons....BY ALL MEANS SHARE! I would love a "spread sheet" of "exceptional mosfets" but I guess @ the end of the day No sensible MFG would go to the trouble to produce a new mosfet that they did not feel was superior in some way to the existing array of mosfets.....and so the task of mosfet selection will continue to be an Ad Hoc process of elimination with "exceptional finds" being time/project sensitive....

Fish

 

[KrisBlueNZ]

Again, Great Catch! But, RDSon is only one spec that makes this particular mosfet really appealing for Low Voltage applications...the extremely low Vgs, Excellent Tf, and very good Tr all combined with exceptional value make me want to find a project for it!

R_DS(on) vs. V_GS was all that I was interested in at the time.

But I am a bit sad that you didn't reveal some "magic" way of ferreting out other exceptional mosfets.....I guess it all comes down to properly "narrowing the field" and then sorting by **something** and then start downloading PDFs .... reading ...... and stopping when you find something that meets all of the requirements....or your eyes start to bleed....I was just **HOPING** for an "Easy Button"....hehehe....

Yeah, that's what I do. If you find the easy button, please let me know too!