Hi there,

I dont want to use the battery connection technique which means I would need 24V battery and I have 12V only. The + and -12V is to power an op-amp and I need the -12V to be generated from the +12V supply (battery wiring techique messes up how the op-amp sees my input signal anyway).

So I have 12V battery pack, is there a convenient IC out there which will help me out? I dont want to build somethig from 'scratch'. I have done some searches but nothing as of yet.

Thanks very much.

 

You did not mention your current requirement. Digikey has a bunch of DC-DC converter modules. List was extensive. Here is one example.
http://search.digikey.com/scripts/Dk...=PT78NR112V-ND

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http://focus.ti.com/docs/prod/folder...cp021212d.html for a DIP solution. It is unregulated but a simple resistor-zener regulator helps out. It will generate equal and opposite output voltages isolated from the input, so as your battery drops the output voltage will still stay the same on + and - output.

Remember, they are unregulated and noisy. You might try the dcp021215d version with linear regulators on the outputs to get very nice + and - regulated outputs.

 

You may want to look at this link
http://www.electro-tech-online.com/g...es-opamps.html

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You can also create a very nice 250ma virtual ground with a BUF634 and two bias resistors, if you are OK with +/-6V supplies.

 

Any opamp will work with a single supply voltage if its input is biased properly.
Look at my STICKY article.

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You can create a charge pump using a 555 timer chip, resistors and caps.

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www.digikey.com has the NJU7662D for $1.67. This IC, a couple of capacitors and you'll have apx -12V unregulated which is good enough for the negative rail of an OpAmp. Another option is just to use a rail to rail OpAmp or the biasing technique Nigel mentioned. It depends on your circuit.

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Please post the circuit, the chances are it can be modified to run off a single 12V supply.

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Thanks very much every one. I will be ordering a -ve voltage generator soon.

Just incase someone knows a way around it,basically, its a non inverting amplifier with a gain of 3. The problem is, its not outputting 0V with an input of 0V. With input=0V it out puts 2 something volts.

 

Please provide more information.

Does the input voltage need to be less than 0V?

Does it amplify AC or is it just DC?

If it's a DC amplifier and the input doesn't need to go below 0V then use a single supply op-amp like the LM358 or MC33171.

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Thanks very much for the suggestion. Planning on getting one tommorrow.