On 17 December 2014 at 20:15, IVP wrote: > > Or how about something like this?... > > > http://www.mouser.com/ProductDetail/International-Rectifier/IRS2003STRPBF= /?qs=3DsGAEpiMZZMvQcoNRkxSQkuprlmO3q%2f%2f34UdbtrJfWmo%3d > > The 130mA of the IRS2003 might be OK (although it seems a > little limp) but if you apply this filter you can do better in the Output > Current department > > > http://nz.mouser.com/Semiconductors/Power-Management-ICs/Gate-Drivers/_/N= -41fcp?P=3D1z0jzfz > > > Usually you don't need vast average gate drive mA - you need around an am= p while the FET is switching but most of the time the gate does not require current to hold it on or off (as long as you do not use 270 R from g to S :-). Gate drive capacitive switching power ~~~ =3D 1/2 C V^2 x 2 x Frequency x = k C =3D gate capacitance. V =3D gate drive voltage two transitions per cycle k is a large enough number > 1 to make it work :-). eg power lost in drive resistors and parasitic stuff and ... . For say Cg =3D 5 nF (highish usually) V =3D 10V f =3D 100 kHz (getting higher than often needed). k=3D1 to start. Power =3D 0.5 x 5M9 x 10^2 x 2 x E5 =3D 0.05 W or 5 mA at 10 V. So 10-20 mA at 10V should suffice here. That's both a high drive frequency and a relatively high Cg so this figure would often be usefully lower. Even 10V is more than you often need. While some FETS only live long and prosper at 1- or more volts gate drive, logic level FETs necessarily need much less, and very low Rdson parts will usually also have distressingly low Vgsmax ratings. Some logic level lower Rdson parts have Vgsmax as low as 5V. A few weeks ago in a moment of madness I stupidly ran a high side PFET (battery shutoff operation, v low duty cycle, resistive load) from a 40 Ah "25V" LiFeYPO4 battery with no zener clamp on the gate and driven by a low side bipolar. Rated FET Vgsmax was 20V. It valiantly ran correctly for several minutes and then expired with magic smoke. Not the sort of battery you want to let get at your electronics. The extra 5V or so over the rated gate voltage proved too much for it. Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .