If he's using the '7301, then it is wasted as a comparator. It would be better to use it for a standard P-MOSFET VCCS where the external turn-on signal forms the input "V" sized for an output "C" of 4 amps, the loop saturates with FET full-on under normal operating conditions, and the limiting could be foldback or hard, with everything wrapped up in a single subcircuit. The only drawback is the weak output current capability of the '7301- wonder why that is so.
But if the fet goes into constant-current mode, it will fry. The comparator thing switches on and off in limit, with much lower power dissipation.
And the gate doesn't need a lot of current. It's ... what do they call it? Yes, "insulated."
John
I can't believe I didn't think of this earlier! Thanks for the hint.
-Mike
We do have, LM385-ADJ low-current type (5.3V max compliance), and the LM4041-ADJ faster high-current (15V max) type.
--
Thanks,
- Win
Hello Win,
Thanks! A bit on the pricey side but it's good to know they are there. The LM4041 could make for a nice and quite precise high side limit in this case, the OP just has to make sure the max anode-cathode voltage isn't exceeded.
-- Regards, Joerg http://www.analogconsultants.com
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