Hi,
I run AC simulation of some opamp in unity gain buffer configuration(open loop response), the open loop gain seems to be usual response with dominant pole at low frequencies, but the phase starts from -180 degree and rising. There is no invertion at DC, can anyone explain such phase behaviour?  

Hi,

Maybe your setup is wrong. Try this;
- connect Vdc (reference) to in_positive
- connect vsin acmag=1 to in_negative (feedback loop branch)
- run dc with closed loop
- run ac with opened loop

You should get a good results then.

L.S.