+2.5/-2.5 power supply from a 9V battery

Hi,everyone

I'm trying to get a +2.5/-2.5 power supply from a 9V battery. But I have no idea where I should begin with. I tried to check different regulators from Digikey and totally got lost. Is there anybody can help me? thx

First use a 5V voltage regulator (7805 or similar) to reduce the voltage from 9 to 5.
Next, use active voltage divider (build around an opamp such as LM358) to devide this 5V into 2* 2.5V .. principle of so called "virtual ground" is on the attached picture. In practice, if you need more current, you will be using external transistors ..
Here you will find some examples on how to do it:
https://tangentsoft.net/elec/vgrounds.html
Regards,
IanP

TiwstedNeurons,

As IanP mentioned, first you need to buck (step-down) the input 9Vrms DC to 5Vrms DC, in principle. But I suggest 5.5Vrms because electric circuits are lossy and you are likely to lose some fractions of a voltage.

Using two capacitors C1 and C2 connected in series, then in parallel to the 5.5V and 0V supply. C2 is polarised with its +ve end connected to C1 and its -ve end connected to 0V. Connect a diode 1N4001 with its anode to 0V and cathode to a node (I call it A) common to C2's +ve electrode. Node A is a virtual ground for +/- 2.5V. 0V is a virtual -2.5V and 5.5V is the virtual +2.5V.

C1 can be a polarised capacitor if you want but the +ve end must be connected to 5.5V.

This method is called the level shifted DC supply, not popularly mentioned because these days more people use Voltage Inverter IC.
Another method is by means of a oscillator using a 555 Timer, generates pulses, filter it to get fundamental frequency or single AC and rectify it to get DC, however similarly uses two polarised capacitors, define a virtual ground for +/- voltage.

Get two adjustable voltage regulators (LM317).
Use one to generate 2.5V.
Use the other one to generate 5V
The 2.5V output becomes your new 0V; -battery is now -2.5; 5V is now +2.5V
DrWhoF

dc-dc converter.
switch mode LC can fit you requirement

Try using two capacitors first as they costs cheaper than buying two LM317 ICs. DrWhoF basically suggested the same principle as I did on the level shifted DC supply.