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I would like to know what circuitry I will need in order to drive a N-Channel MOSFET (IRF1405) with the load placed on the source.

From my understanding the laod is placed on the drain however I would like to build a H-bridge driver with ONLY N channel mosfets. The high side mosfets of the bridge would therefor require some method of driving the MOSFETS properly.

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  • \$\begingroup\$ A typical MOSFFET H-bridge. You need a mosfet/igbt driver with separated psu or to use bootstraping technique. look for IR2112 and similar. Keep in mind that bootstraping needs switching of transitors all the time, so maybe you can't acheive 100% duty cycle ratio. \$\endgroup\$ – Marko Buršič Jan 22 '16 at 12:09
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Use an appropriate driver. Here's just one of the many available: -

enter image description here

It basically works like this: -

enter image description here

It creates a voltage (Vboot) that is several volts higher than Vbat. This allows it to properly drive an N channel MOSFET used in the upper half of a half or full bridge motor controller.

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    \$\begingroup\$ Not to be overly annoying, but I'd like to add the minimum switching frequency requirement for the bootstrap by way of this comment. It's only visible in a tiny hidden corner of the typical application "6Hz to ..." and the OP might be hunting for near-DC functionality. In which case, of course, a separate 5V booster circuit can be used to supply the boost pin of most of these drivers with "Vcc + 5V". \$\endgroup\$ – Asmyldof Jan 22 '16 at 12:48
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    \$\begingroup\$ @Asmyldof good point - my answer assumes that the H bridge is being toggled quite regularly a la PWM. \$\endgroup\$ – Andy aka Jan 22 '16 at 12:53
  • \$\begingroup\$ It is the most common to use PWM. I only note it, because I have recently been required to include some all-N H-bridges for polarity control in a design and very quickly decided on a VQFN H-bridge driver as you suggest, but with a tiny SOT23-6 cap-cap booster to make 17V on the 12V system for the BOOTSTR pin. \$\endgroup\$ – Asmyldof Jan 22 '16 at 13:07
  • \$\begingroup\$ @Asmyldof could you elaborate futher on how I can do this using a Bootstr pin? I think this might be the better approach for my application \$\endgroup\$ – user3095420 Jan 25 '16 at 7:49
  • \$\begingroup\$ @user3095420 exactly as I described. You make a voltage 5V above the supply if, and only if your driver device supports that and connect that to the boost pin in stead of the capacitor. \$\endgroup\$ – Asmyldof Jan 25 '16 at 8:04

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