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Generating negative VDC for Op-Amps

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tomroth

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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?

Thanks!

Tom
 

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.
Tahmid.
 

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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