i am doing a project using cuk converter.I need to change the output from negative to positive(-30v -+30).I have used op-amp741,which gives maximum of 10.75 only.kindly give me a suitable solution.

 

Here's the basics on a Ćuk converter:
http://en.wikipedia.org/wiki/Ćuk_converter

I don't see where a 741 opamp would come into the picture?

Where is your schematic?

 

I have designed cuk convertor separately.The output is negative ,but positive output is needed for our project.For that i have implemented inverting amplifier (741),its maximum output in datasheet itself is 10.75v,But i want more than 15v.kindly provide suitable suggestion.

 

A 741 opamp is a very old design.

However, it should still be able to get within 3v of the positive rail, but typically within about a volt - unless your load is less than 10k Ohms.

Since you say you have already made a Ćuk converter, and it's output is negative, what is the voltage of the positive (supply) rail that you are starting off with?