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As has been stated, to properly turn on a MOSFET the gate-source voltage needs to typically be 10V, or 10V greater than your source voltage. That's why N-MOSFETs are not normally used for positive output buck converters, since that gate voltage needs to be 10V above the input voltage. If you use less voltage on the gate in a follower mode, there will be a significant voltage drop across the transistor when it is on, increasing it's dissipation and reducing the power supply efficiency.i seee.. so this configuration its not that good... but what i want to know is why does it work? can you tell me from this configuration. how do i calculated what is needed to turn on/off the nmos in source follower mode?
because my circuit is a buck converter.. the output voltage will be lower.
A PMOS should work.i know what you mean but i dont know why that circuit configuration didnt work with a PMOS.... ive built it on a breadboard it didnt work however, in simulation it worked quite well. the problem back then was that when the gate was driven to mebe +15V +0V the drain voltage of the PMOS only outputs 0.5Vpeak to peak. so it couldnt switch on/off. I really dont know the reason why... i then cahnge it to a NMOS with a source follower circuit then my buck converter works.... lol....