Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
Offset consists of two parts, systematic offset and random offset. Systematic offset is due to mismatch in device sizing, currents,non symmetry,etc. Random offset is due to device property mismatch such as Vt,effective W,L.
For any opamp designed symmetrically, there will be no systematic offset. Random offset is a statistical parameter, depends on the statistical variation of the device properties.
Of course in an ideal opamp, there is no systematic or random offsets and hence no offset.