Hi,

I have some problems to understand the initial condition for a straight line approximation to the phase of a bode plot.

For example, we have a straight line approximation to the phase bode plot that starts at-180 degree.

What does it implies in term of number of zeroes and pole at ω=0[rad/s] or initial point.

what if instead of -180 we had180 degree , 0 degree?

I know that if a plot starts at -90 degree , they must have a pole ((if the constant of the transfer function is positive),

and a zero if the initial phase is 90 degree (if the constant of the transfer function is positive).

Thank you

B