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Generating negative VDC for Op-Amps

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Jan 30, 2011
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Hi all!

Just a general question. Many Op-Amps require positive and negative voltage to operate properly. What is the best way to generate the negative DC? I used a 555 timer with a bunch of resistors and capacitors to generate negative DC and sent that to a 7905 regulator to get -5 VDC, but that was a bunch of work. Any suggestions for an easier solution?



MPS MP1530 can provide both positive and negative voltage rail.

Opamps have pretty much always been able to work off of a single supply. even "dual supply" opamps can. The only issue is that they are not optimized for such operation. Particularly in terms of working with very-low supply voltages, inputs near -Vee (0V), and outputs near -Vee (0V).

There are also issues with operating any opamp with a single power supply, especially when a signal extends to DC. This is because to use an opamp with a single supply, a DC bias must be added and possibly removed at a later stage.

a variety of charge pumps exist that can give you a negative rail if one is really justified.

Simple charge pump consists of 4 resistors, 2 bjt's and 2 capacitors for generating square wave and then additional 2 bjts, 2 caps and 2 diodes for pumping circuit. I made something like that on 25 x 27 mm single sided pcb. I guess it could be miniaturized even more with a proffesional-made pcb. U could also swap discrete oscillation circuit for ne555 in standard application.

You could use ICL7660. I used it quite a few times and it's quite a common chip.

**broken link removed**

Hope this helps.

Just used the TPS60400 from TI on a project. Very cheap, very easy to use and just three externals caps!

Cheers, Marcus.

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