I'm sure this question has come up before... I need to convert +5V from my power supply (a USB cable) to -5V to drive the negative supply of some op-amps. I found a couple of circuits that do this by converting DC to AC with a 555 and rectifying it: http://www.ecelab.com/circuit-polarity-inv.htm http://www.aaroncake.net/circuits/vinvertr.asp http://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm Trouble is, I'm not sure if these circuits can supply enough current for what I need. I have three op-amp ICs (two LM324s and one LM339) and will use all 12 op-amps. The LM324 datasheet says '0.18 mA supply current per channel' and the LM339 datasheet says '0.2 mA supply current per channel.' So, since I'm using all 12 channels, I believe the op amps will draw (0.18*8 + 0.2*4) = 2.24mA total. The circuit in third link can supply 12mA, so I would assume the first two could supply at least a few milliamps. Is this feasible? Would I be better off getting a DC/DC converter? There are so many options that I wouldn't know which one to choose, and they're not cheap. I'm probably just going to wire up each of these circuits and see what I get. What's the worst that could happen if I wind up drawing too much current from the 555?