Paul, Thanks for the clarification. Not having a hardware background, I tend to envision the battery "pushing" the current through the circuit, rather than the device "pulling" the current it needs. If I could only keep that in mind, I could probably answer a lot of my own questions without having to bug you guys and gals. Thanks to all for your responses to my questions on this and the 2N5192 question, Adam On Mon, 17 May 1999 21:04:59 +0100 Paul Fletcher writes: > Adam, > > In the example below the 7805 reg will have to dispose of > (12v - 5v) * current passing thought it. The key point here is the > current passing thought it - not what is available at the supply. > Therefore if you have a PIC and a bunch of logic, LEDs, blar, blar > all on the 5v supply and these are drawing, say, 200mA then the reg > will have to dispose of 1.4 watts of power as heat, > (12v - 5v) * 0.2A. The switch from linear to switching you have to Adam Bryant (age 0x23) abryant@peaktech.com (work) adamdb@juno.com (home) Parker, CO, USA Robotics, RC Airplanes, anything using a PIC ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]