On Wed, Jun 3, 2009 at 2:06 PM, Mike Harrison wrote: > On Wed, 03 Jun 2009 15:38:25 -0300, you wrote: > >>Mark Rages escreveu: >>> I need a P-channel to switch a ~20 mA load. =A0 System supply voltage i= s 3V. >>> >>> Good ol' BSS84 has a threshold voltage of up to 2V, =A0and looking at >>> the curves it looks like it might not switch hard enough with 3V >>> drive. >>> >>> What part are people using for this? =A0I prefer to spec cheap, common = parts. >>> >>> (A saturated PNP would work, but I need to watch quiescent current in >>> this battery-powered application.) >>> >>> Regards, >>> Mark >>> markrages@gmail >>> >> >>What MCU are you using? >> >>Many PICs can supply up to 25mA per output pin. > > At 3V you will probably get a noticeable voltage drop though. If you can = low-side switch =A0PIC O/P or > N-Fet) , you'll get less drop at lower supplies. > > I tend to use Zetex ZXM61P/N02 or 03 as a general-purpose small FET - ver= y fast and can take about > an amp (as long as you switch it nice & quick, before it pops!) > I'm using an MSP430 (I could use something else I guess -- no firmware written yet.) MSP430 has less output drive than PIC. Mike, I was looking at that Zetex part. It's more expensive than I expected, about $0.20 in 1k. I guess that's cheap enough though. Regards, Mark markrages@gmail -- = Mark Rages, Engineer Midwest Telecine LLC markrages@midwesttelecine.com -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist