one question: what is the
one question: what is the (on the schematics of “Simple P-channel over N-channel h-bridge” or “BOAs brillinat h-bridge”) mosfet driver for? i tried to read the datasheet but can’t understand its function.
Robologist put that in. My
Robologist put that in. My understanding of it, is that the driver allows a larger amount of current to the MOSFET gate. I have a H-Bridge which currently is not using a driver, the gates are switched with TTL voltages, but I can imagine - that depending on your setup you might want to use one. I chose fewer components and have not run into any white smoke … (yet). 
GroG
MOSFET drivers for PWM, fast switching
MOSFETs need to be switched on quickly and off quickly to keep from being heated up. The longer time is spent in switching, the more the FETs are in a linear region where their resistance is much higher, causing power disspation. Getting them to switch faster requires getting the voltage changed on the gate quickly, which essentially acts as a capacitor. To charge a cap quickly means to send a lot of current to it quickly. Typical logic gates from micros, are only good for 5 to 20 mA, where a driver can push in the Amp range. When trying to switch faster, more current is needed, so where a micro tied to a gate of a MOSFET might be able to switch it at 1 kHz ok, going any higher might cause the FET to heat up as it stays more in the linear region, never completely turning off or on. Additionally, FETs switch better with a gate voltage about 10 volts above the drain level, rather than 5. There are "logic level" FETs but their operation is quicker when used with a higher voltage. THere is an upper limit on that, typically at 20 volts or so.
thank you very much, great
thank you very much, great explanation.
I am walking in the big
I am walking in the big footsteps of the mighty CTC. I have accepted the challenge of building BOA’s hybrid H-bridge motor driver.
Just like Chris I’m going to control it with a picaxe.
I will be asking questions in the near future.
Thank you very much for
Thank you very much for these great information,well appreciated
cheers!
this is fantastic! i might modify this circuit to make my next robot!