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I am building an H-bridge motor control for DC motor . I am using "SQD40N06-14L_GE3 " N_channel MOSFET. Did i have to add a rectifier in parallel with the mosfet (the mosfet already have one integrated).Thanks

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  • \$\begingroup\$ What current will the DC motor draw? \$\endgroup\$ – Huisman Apr 19 at 15:34
  • \$\begingroup\$ The DC motor will draw up to 20A. \$\endgroup\$ – B.walid Apr 22 at 10:43
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The internal parasitic body diode of the MOSFET can be used, but will not be optimal since it's a byproduct of MOSFET construction (too slow, not soft recovery, inefficient). The body diode will be insufficient for some projects. A very few MOSFETs try to optimize the body diode a little bit to reduce overall component costs in a project, but >99% do not.

I always use external diodes.

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    \$\begingroup\$ It may be worth mentioning that some mosfets, especially power switching devices, have an antiparallel diode on a separate chip in the same package, specifically to give a well-characterised source-drain diode. I've seen this in power modules, at the very least. \$\endgroup\$ – Hearth Apr 19 at 15:49
  • \$\begingroup\$ I've seen this in a few smaller MOSFETs too where a schottky diode is incorporated (I don't think it's a body diode made to be a schottky, or if that is even possible , but I don't really know) \$\endgroup\$ – DKNguyen Apr 19 at 15:50
  • \$\begingroup\$ As far as I'm aware, it's not possible to make a FET with a schottky body diode. Many FET symbols draw the body diode as a zener, however, which may be what you're thinking of? They have similar symbols. \$\endgroup\$ – Hearth Apr 19 at 17:33
  • \$\begingroup\$ I'm just saying I don't know whether it's a discrete schottky diode (body diode is still there just no one cares about it anymore since the schottky is also there) or they somehow turned the body diode into a schottky. I tend to assume the former. But the MOSFETs that do this are not discrete about it; It's a very clear selling point of the device so it's definitely there. \$\endgroup\$ – DKNguyen Apr 19 at 18:11

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