I'm using an IRF620 MOSFET paired with a TC4420 high speed gate driver. Just using the MOSFET by itself with the Arduino does not work properly. It works a lot better and faster with a gate driver.

What I'm confused about is firstly why the MOSFET just does not work with normal logic levels. Maybe I'm getting things confused but isn't the VGS the aspect you should be looking at to determine if MOSFETs can be used by logic level components? Why then is the IRF620 sitting at 4V/0.25mA on the below datasheet but does not work when connected to a digital pin of an Arduino, but works with a 6A gate driver?

Maybe I'm looking at an incorrect datasheet for the MOSFET? I'm unsure, but these are the links:


1 Answer 1

  1. The IRF620 is not a logic-level MOSFET, it requires VGS= 10V to get a guaranteed low Rds(on) of 0.8\$\Omega\$ (not that low, but it's an older design of relatively high-voltage MOSFET). If you only need it to conduct 0.00025A with 4V drop allowed across the MOSFET, then use the 4V number. That would be a bit of a waste. You won't likely find a logic-level MOSFET rated for 200V.

  2. I don't see a gate charge specification in your linked datasheet, however the Vishay datasheet for that part number has a maximum gate charge of 14nC under specified conditions. That charge must be supplied by the driver. If you don't care how fast it switches, a high current driver is not necessary, but if you need it to switch quickly then you need to slam the gate with a lot of current in or out. Switching slow causes heating of the MOSFET during the switching, and can violate the SOA (see my linked datasheet) if the load is high current and the switching is too slow, causing immediate or eventual failure.


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