For the circuit of opamp 741. we have to supply the dual power for it. How can I make a dual power supply from single. For example, make a (+9V)-GND-(-9V) from single 9V battery ?
You can use the ICL7660. It takes a positive voltage (up to 12v) and generates the inverse:
Very easy to use, I've used it in several commercial products.
If the ICL7660 chip is difficult to find, you can also roll your own" charge pump inverter" using a 555 timer, which should be available anywhere, and a few extra components:
There are lots of variations on this circuit, not just for generating negative voltages but also voltage doublers and triplers too. Just do a Google search for "555 charge pump images".
You could use an isolated DC-DC power supply module. They only require an unipolar voltage source to generated the two voltages rails (-9 V, 0 V and +9 V for your application). These module are small enough and are usually in a friendly SIP or DIP format. Except for decoupling capacitors, they do not need any external component to work.
However, be sure to use the good decoupling capacitors that are recommended on the datasheet and be sure to choose the module that can provide enough power. The module operates at a fix output voltage so be careful to select the correct output voltage for your application!
These modules are sold by differents manufacturers like XP Power, Cui and Recom power.
If you use Digi-Key to source your components, these modules are found in the Power Supplies board mount section and then select the isolated module type.