Your simulation shows your are using 400kHz for your PWM frequency. All three of these ICs are to be referenced (connected) to your circuit ground - unlike the V2 of your schematic. High side driver ICs, half-bridge driver ICs, and synchronous buck converter driver ICs do just that via level shifting and a so-called boot-strap capacitor. For practically any other FET, V_GS should be a minimum of 10V. If you use a 'logic level' FET, V_GS should be a minimum of 5V. This fact will mean the GATE voltage will be greater than the DRAIN voltage when your FET is turned on. To turn on a FET: Returning to your Multisim schematic, the negative-most terminal of V2 is NOT to be connected to ground, instead it is to be connected to the SOURCE of your FET (V_GS). You can ignore PWM_LO and Q3.2 and you can use your 1N5820. The App note suggests a synchronous switching. I think you will find the app note applicable. 3.)Take a look at TB3103 as innertwist recommended 3 weeks ago. all have a buck converter IC you can fairly easily and efficiently use to deliver 2A from a wide input voltage range (42V, 60V, etc.). For that matter, find an off the shelf, isolated AC-DC converter. If you need 2A I recommend one of the following (In THIS order if you have not made much progress in a while): 1.)Acquire an off the shelf DC-DC converter. ![]() You could specify a PNP to deliver that much current, but a FET would probably give you less grief, especially at 400kHz.
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