Fet Drive Circuit With Pic Micro

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Can’t you just use a logic level FET like IRL520N or IRL3103 on the low side and treat it like a gate?
 
ClydeCrashKop said:
Can’t you just use a logic level FET like IRL520N or IRL3103 on the low side and treat it like a gate?
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You can but trying to PWM a FET with only 20mA of gate drive would burn it up.

D.
 
Current is also needed in order to charge up the gate-source capacitance in a FET in addition to the gate voltage. So although you can switch the IR520N on with a logic level, you cannot switch it very fast since it's GS capacitance is too high for the current that can be sourced by a PIC. It needs to be a small, logic level FET with low gate capacitance.
 
I'm not sure who you are responding to here. I have been saying that...Mind you, there are no FETs such as what you describe that will switch the currents that the ones that were listed earlier can.

D.
 
Thanks for all your help with this, just one more thing to query before I implement it,

Are 2N3904 and 2N3905 transistors suffice for the switching currents involved?


Both can handle 200mA, thats 100mA more than the BC550 and BC558 in the diagram I supplied on my original post
 

It is very much a case of the more the merrier, however for what you are doing they will probably be fine.

Dan
 
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