#### merenguelee

##### Newbie level 4

When I did analog design recently, I got a frequency response of a system like this(I have slightly simplified the plot):

The phase margin and gain margin printed by the

**Virtuoso**are 80 degrees and 10 dB.

What I'm

**confused**is:

- based on the theory I have learnt, the phase has shifted 80 degrees at UGB frequency compared with low frequency, so the phase margin should be 100 degrees rather than 80 degrees, right?

- also, the point we get the gain margin should be the frequency when the phase crosses -180 degrees or 180 degrees, but it seems that

**Virtuoso**considered the frequency at which the phase crosses 0 degree as that frequency and then got a 10-degree gain margin.

Now, I doubt myself a little bit, so I post these to confirm with you guys.