On Thu, Jul 26, 2018 at 07:20 AM, satbeginner wrote:
So, my (probably) premature conclusion is: the FET I ordered should work fine.
It's capacity does not have any effect on the rise-and-fall times, it's own
turn-on time is way smaller than the applied pulse, and the ON-resistance is
lower, so dissipation should be lower.
Yes, my gut feeling too : from the data I collected previously, basically the worse FET's have about twice the gate charge than desired. So even if the driver circuit had zero headroom to drive that extra charge, it means the rise time would double, so twice the power dissipation. But RDson is about 10 times lower, so 10 times less power dissipated... so overall the power dissipation would be, at least, 5 times less. Back of the envelope calculation of course, but sounds half reasonable to me...
So yeah, basically pretty much an modern FET would work then...
Still, it's always interesting to learn more about the design aspect of things, understand in enough detail what parameters need to be considered... measure things, quantify things... so we actually understand what we are doing/what's going in the circuit.. rather than just slap some FET, see the scope come back to life and call it done ^^
But... as interesting as it would be, I have other stuff to do in the lab at the moment.
Would be nice to have an actual engineering familiar with this stuff, to tell us all about this. Where we are wrong, what we have failed to consider/take into account etc... boy I miss school time, was great to have a couple electronic teachers I could bombard every day with all my technical questions...
Now I am on my own, making guesstimates on a forum ! LOL
Still, keeps my brain going...
Vincent Trouilliez
Vince