I wrote: >I'm searching for a low-cost negative 5V regulator that is >reasonably accurate. Something similar to National's LP2950A but >for a negative rail would be perfect. I appreciate the suggestions that I've received. At 06:28 PM 12/22/2009, Mike Harrison wrote: >for 10mA you could probably use a reference and an opamp. >If you already have an accurate +5v rail, a simple -1 gain inverting >amp configuration may be >sufficient. I don't already have an accurate +5V rail, unfortunately. I'm also limited by space - this is a through-hole-parts design and don't have enough space for an op-amp and reference. At 07:24 AM 12/23/2009, Spehro Pefhany wrote: >Assuming power consumption is not a big concern.. >Resistor + shunt reference. As two-wire devices they don't care about >plus or minus, provided of course that they are connected the right >way around. My standard power supply for most of these applications is a zener diode and resistor. I avoided that this time because of the poor initial accuracy (5%) of the standard parts I use ("B" suffix 1n47xx, 1n52xx). >One example would be the TL1431 (0.25% accuracy) with a couple of resistors >(or use two in series!) Or the LM4040-5 (no resistors, but only good for 15mA >forward current, so there is not much to play with on the high end). I have to confess: I didn't even consider using the TL431 - I use them in other products and they are about 2% accurate. I wasn't aware of the TL1431 until you mentioned it - initial accuracy is 0.4% - excellent! I've got about 7mA current available (worst-case lowest possible input supply) and the PIC and all associated circuitry) needs less than 4mA, so there is sufficient headroom. I'm going to give this one a try. Many thanks! dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist