hi ... I am interested to know if it is safe for me change job after I get my employment authorization document (though the field of work will remain same in general).

Is there any time limit or should I wait for my green card.

The way I understand it, the EAD authorizes you to work in the US, not for just one employer. Anybody else?

Be very careful - Theoretically, you are supposed to wait 180 days (portability ruling) before you change jobs and then the new company needs to continue with the sponsorship.

I think the 180 day ruling over applies to the I 485 and movement is possible with an EAD. check with an attorney