Direct Gate Drive with PIC - Electronic Circuits Projects Diagrams Free

dknguyen · 15th March 2008, 05:31 PM

I'm revisiting making a replacement PCB for some servos. I don't normally ever try and drive a MOSFET gate directly with the pin of PIC and have always used and told people to use gate drivers. But I'm really REALLY tight for space and these transistors are so small they have a really tiny gate charge. For the rise times I want, I only need 20mA of drive current, but that's kind of hitting the limit for a PIC pin (which also has other things to do rather than just sourcing that pin).

Does anyone have any experience? I'm a bit of afraid of burning something out because a pin is sourcing/sinking too much current

dknguyen · 15th March 2008, 06:29 PM

Ah screw it. I think I can add on a drive BJTs for the PWM FETs.

theinfamousbob · 17th March 2008, 06:15 PM

Quote:

Originally Posted by dknguyen

Ah screw it. I think I can add on a drive BJTs for the PWM FETs.

Sounds like a safe plan. Why not use SOT-23 package transistors if you're pressed for space? If they only need to source/sink 20ma I'm sure you could find one that will work.

dknguyen · 17th March 2008, 09:49 PM

Quote:

Originally Posted by theinfamousbob

Sounds like a safe plan. Why not use SOT-23 package transistors if you're pressed for space? If they only need to source/sink 20ma I'm sure you could find one that will work.

Because I'm just that tight for space. We'll see.

15th March 2008, 05:31 PM	(permalink)
dknguyen Experienced Member	Direct Gate Drive with PIC I'm revisiting making a replacement PCB for some servos. I don't normally ever try and drive a MOSFET gate directly with the pin of PIC and have always used and told people to use gate drivers. But I'm really REALLY tight for space and these transistors are so small they have a really tiny gate charge. For the rise times I want, I only need 20mA of drive current, but that's kind of hitting the limit for a PIC pin (which also has other things to do rather than just sourcing that pin). Does anyone have any experience? I'm a bit of afraid of burning something out because a pin is sourcing/sinking too much current

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15th March 2008, 06:29 PM	(permalink)
dknguyen Experienced Member	Ah screw it. I think I can add on a drive BJTs for the PWM FETs.