Hello all, I'm putting together an HBridge to drive some automotive motors (5-10A), and am selecting MOSFETs for the bridge.
It seems a classical pick is the IRF540/IRF9540 pairing. These have ~30A current handling and turn fully on in the 10V range, which seems appropriate for the car battery. I'll use some darlington transistors (tip120/122) to drive these from Arduino.
So, perhaps you have different suggestion from these, but even within IRF540, there are 8 or so versions in T220 package on Mouser. These range in price from $1-$4. I'm trying to figure out what accounts for the price difference... I'm assuming that the higher priced ones have some desirable quality but I can't quite tell what it might be. I've been looking at the parametric charts, but honestly my eyes keep crossing and I'm not spotting anything obvious. In fact some desirable qualities seem better in the cheaper one.
Here's the expensive one: http://www.vishay.com/docs/91021/91021.pdf
Here's the cheaper one: http://www.irf.com/product-info/datasheets/data/irf540z.pdf
The cheaper one has a lower power dissipation capacity but then has a significantly lower Rds(on), so perhaps doesn't need it. I'm not building enough of these units for the $3 to matter too much, but would like to learn more about why one would pay 4X for the Vishay unit?
Then... there's a "middle" version, which is $2.75 or so - actually, while both of the above have 500 units in stock, this one has 16,000 units in stock, so seems like it's the highest seller:
By the way, one more question - is the 9540 the best match with the 540? Their Rds(on) currents seem fairly different, so should I expect materially different motor speeds with this pair (speed isn't really that important to this application)? I can't understand how to easily pick a better pairing as slogging through the part selectors and their crappy rows and columns is very slow going. Why aren't these in some kind of interactive graphic package so I could filter all of the parameters continuously and just have what I need pop out? Anyone know of a good part selector like that?