Gate Driver Design for irf840

IRF840 is a low power MOS. Instantaneous current of the gate is small depends on parasitical resistance and capacitors of driver . One can use a pair BC327/337.For drivers looking for www.irf.com schemes. And on net too. Have many applications at that address.

Unless you need fast switching, below 50ns, it's customary to add a series gate resistor to slow down the switching and avoid inductive V = L di/dt spikes, which can damage the MOSFET's gate and cause other problems. If you add a say 47-ohm resistor, that will limit the current to about 100mA, and you can use a simple transistor circuit for gate driving. But in any case you will need 10V or more for the gate-drive voltage with an IRF840 or any other 500-volt type.

But if you do need fast switching, or to obtain a 10 to 12V gate drive from a logic input, then definitely use an official gate-driver IC. There are plenty of cheap ones available, such as the classic TC4426 (datasheet link) dual inverting 1.5A driver, or TC4427 (noninverting), $1.39 each at Mouser.