Splitting a single Vcc power supply into bipolar Vcc/2

lm358 virtual ground

Hello,
I want to design a simple circuit to generate +4.5 v and -4.5v from a single 9 volt.
I'm designing a small circuit, and instead of building my own power supply i decide to buy a regular 9 volt dc adapter as a power supply.
I want not to use batteries to guarantee a long life power source.
But some ic's i use need split supplies.
Also generating ±6v from 12v adapter will be good.
I'm not sure if dc adapters generate a regulated voltage or not.
If not i think i should use regulators to get a clean voltage. Write?
Finally, The whole circuit is low power and draws low current. But i haven't calculate the current exactly. I'm now using a computer power supply as a test.
Thank u so much.

vcc power supply

Any opamp works from a single supply voltage if its input is biased at half the supply voltage. The input, output and feedback common might need coupling capacitors. Post your circuit for us to show you how.

Most AC to DC adapters are not regulated. Their voltage varies all over the place and they have hum when loaded.
Ordinary voltage regulators need an input voltage about 2V higher than their output voltage. Low dropout regulators need an input voltage that is 0.5V more than their output voltage.

bipolar power supply schematic +4.5 -4.5

I've found this circuit.

**broken link removed**

I wanted to share it with others.
what's ur opinion about it. Is it good.
And what about 1458? Is it LM1458.
It's a dual opamp. Is it noisy or good?
Can i use LM358 instead?
Will this circuit work well as a whole ?
Thanks in advance

splitting a single power supply

What is the circuit that will be powered with plus and minus 4.5V?
Post it and we will show you how to bias it so it works with only a +9V supply.

circuit to split a single power source into 2 dc

My circuit diagram is not ready right now. I don't have a soft copy of it.
I thougt that it's easy to explain the splitter circuit to me, which i may use or apply for any general circuit not a specific one.
Just like the circuit i've found and mentioned before. I think this circuit have one problem that it doesn't mention the power or current limit. Right?
Thank u so much & sorry for the disturbance.

voltage splitting 9v 4.5v

The shown active virtual ground generator must be expected to be unstable (depending on the output capacitors ESR, respectively the presence of additional bypass capacitors) and generate small interferences in the kHz range. An additional compensation is necessary to achieve unconditional stability. Furthermore, two OP's should never be connected in parallel in the shown way, they are sourcing short circuit current towards each other due to offset voltages.

Alternatively. the inverting input of each OP can be connected to it's output, using the 10 ohm resistor to isolate the load. The resistor can be lowered to 1 or even 0.1 ohm to reduce the DC output impedance of the virtual ground generator. With two OPs, the minimum suitable value also dependends on the maximum offset voltage of the amplifiers.

As a prerequisite, the OP should offer internal safe current limit, most general purpose OP have.

9v bipolar 4.5v split

Thanks FVM,
So i may apply this circuit as it is except for adding a 10 ohm resistor in the feedback path of each opamp,( i.e between pins 1,2 and pins 6,7).
Is that right?
Should this resisrtor have the same values with R3 & R4 or it's not important.
The last thing, what about using LM358 dual opamp. Is it good.
Would it be better by using regulators. I need some help in using them.

Thank u so much for ur time.

schematic single to bipolar supply

You might not even need a voltage splitting circuit.
I have asked for you to post the schematic of the circuit that needs to be powered but you don't.

Please explain what the circuit is for. Audio? Video? Lighting LEDs?

generating the vcc/2

You could look at the TLE2426 ("1/2 RAIL VIRTUAL GRND") from TI.

As audioguru suggests, it would be clearer if you defined what you wanted.