On Thu, Aug 6, 2009 at 11:08 PM, Chris Loper wrote: > Why is 'a true totem pole MOSFET driver' necessary? > Could not a small logic level FET driven directly from a PIC pin drive the power FET? > Imagine that the MOSFET gate is one end of a capacitor and the other end goes to ground. Now imagine that you need to charge this capacitor up to 10v to turn it on -- and down to 0v to turn it off. If it's a simple capacitor (we'll say it is) then it might be around 4 nanofarads and let's assume you want to turn it on or off in 200 nanoseconds. This means you need an average current of: I = C*dv/dt = 4nF * 12v / 200nS = 240mA This sounds about right but I would make it 2 or 3 times higher because I wouldn't want the MOSFET to hang around in it's linear region for any longer than necessary (and it's not a simple capacitor). You can (probably should) do some reading on MOSFETs. -- Martin K. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist