how to convert a square wave output from SG3524 to sine wave using op-amp or...

[EMMANUEL TOM]

Perhaps you can configure the SG3524 to input a sinewave of the desired frequency, (I assume 50 or 60Hz), such as from a phase-shift sine-wave oscillator, to the IN+ or IN- inputs to generate a PMW sinewave modulated output.
This output can be LC filtered or run through a transformer to give a power sinewave output at the oscillator frequency.
Here's a circuit that attempts to do that but it apparently has some problems with the output circuit.

Please Post the LC filter circuit diagram if you have

 

[spec]

Hi ET,

You would never be able to build anything as cheaply as this for example: https://www.ebay.co.uk/itm/2000W-Ca...4ed5280&pid=100005&rk=4&rkt=6&sd=201607696071

spec

 

[crutschow]

Please Post the LC filter circuit diagram if you have

It's simply a series inductor with a capacitor to ground at the output.

 

[ronsimpson]

 

[EMMANUEL TOM]

Thanks crutschow , let me try it...