how to caculate the phase degree by spice ??

[titanchen68]

I have read a lot of thread about feedback discussion.
Some talk about phase degree by using spice...
could anyone teach me how to spice it ???
how to feed the signal and how to caculate the phase ??

now i build my class-d using post filter feedback ....
The phase degree seems very important...

some thread said the phase need to more than 45 degree...
does the phase less 45 degree will get unstable??? but why?
what books i can read about it ???
might anyone help me ..... thanks a lot ...