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Simplest way to get dual supplies for Analog circuits

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srobertjames

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Given a single 9V battery, what's the best way to get split supplies for analog circuits? (Using a voltage divider has 2 disadvantages: wastes lots of power, and not regulated.)
 
The resistive divider doesn't usually need to be regulated. It just needs to be 1/2 of V+ which could be regulated or not. To reduce power consumption, you could use an OpAmp to buffer the divider. It really depends on the circuit though. For example, if you wanted to draw a lot of current between V+ and "ground" and needed a low power negative supply, then a ICL7662 or equivalent would be a better choice.
 
Take a look at the MAX1721.

It requires two external electrolytic caps of 1µF and puts out a maximum current of 25mA at output voltage-1*Vin.

Splitting a 9V battery supply into symmetric ± 4.5V will probably not suffice for many applications.

Supply voltages range from 1.25 to 5.5V.

For more output current and higher input voltages use a SIL DC/DC converter. They are available regulated/unregulated from 1W to 3W (3W types DIL package).

SIL-5 datasheet attached.

Inputs and outputs are isolated - reversing the output voltage it will be negative.

Boncuk
 

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For low power applications, although its probably not ideal, I tend to use a max232 equivilent to get +/- 10V rails. Its pretty easy and means you can use opamps which can't go to either rail, using a 5v supply. There are also several charge pump IC's which can invert or double the voltage, much like the max232 except they have lower output imedences (+/- 25mA) and wuth an LDO, you can regulate these rails.

Only thing is, these converts have noise, sometimes in the audio range, which can bleed into your inputs/outputs. I did make a fairly decent 2W switch mode supply for low power that takes in anythigng from 3 to 9V, and kicks out +/- 12V using a coupled inductor (and a few transistors) - but thats hardly simple, and overkill for most situations.

If we're tlaking prototyping, might be an idea to invest in a dual output wall wart, with some regulation and filtering.
 
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