My Hall effect slide pot throttle works very well. I built the Forrest Cook PWM circuit and mated them. (both diagrams attached for reference)

My diagram shows the comparator stage and my output section with brake FET and its adjustment control.

My question is why does it blow the source FETs when I use a high current motor? No issue with a low current motor. The high current motor pulls about 3 amps at 3 volts free running no load during brush break in. How many more amps would it pull under heavy load at 13V? it is fused at 30 amps and has not blown a fuse. I do not know exactly how much current the big motor pulls.

Does the circuit look reliable? Any obvious improvements? (I am stuck with the high side layout. The motor is grounded That cannot change)

 

I upgraded the pfets to SUP 90s and so far it is working well even with a high current motor.

HOWEVER....I now realize an issue with this high side circuit: the LM324 is not a high rail op amp. (V+minus 1.5) It doesn't return the gates high enough for good cut off. (SUP 90 pfets minimum th -1)

Oddly, I don't notice heat or measure any leak through in the off mode. (single digit mVs at the output when the unit is parked. gates at -1.27)

Questions: am I correct thinking I need a better (RR) op amp for a high side circuit?
Or am I wrong...if it's off it's off. leave it alone?

 

You could add pull-up resistors from the p-fet gates to the +ve rail.

 

Greetings Alec...I tried your diode pullup suggestion with my linear version of this is another thread here. The thing I didn't like about it was that the op amp then does not go as low. This motor is being raced so I need every columb (lol).

I got cleaver and set up an analog switch IC DG419 so the gates can switch up to vcc in the off mode. Houston...we have cut off! .