Pole Zero analyses in cadence

[Junus2012]

Dear my Mentors,

I am performing pole and Zero analyses for my amplifier, after simulation I saw a lot of poles and zeros which are not supposed to appear, I would be sure about it because my frequency gain loop is very clear behaving as single pole LPF,
I have enough phase margin so even the nearest pole to the GBW should be far.
While the pole zero simulation giving me some poles and zeros in my flat area.

May be my test bench and and simulation setup is not correct, could you please suggest me

Thank you in advance

- - - Updated - - -

I am connecting the amplifier in unity gain connection to have stable DC operating point,

I run only the PZ analyses with this setting

 

[vivekroy]

Can you give an output of the pole-zero plot?

 

[sutapanaki]

What is supposed to be the value of the max frequency in your second picture?

 

[Junus2012]

Dear friends tomorrow I will post the simulation result,

But the test bench setup is correct ?

Thank you once again

 

[Junus2012]

Hello

I would believe there is mistake either in the test bench setup or the simulation setting,

these are the result I got from AC and Pole Zero analyses

this time in the simulator I didn't sweep the frequency, I kept it constant

Any way, when I choosing the input source voltage for the setting, I am selecting the AC source

 

[t4_v]

@Junus2012, are you afraid of poles and zeros? You're AC characteristic looks good. You have almost 80 degrees of phase margin and gain plot looks also nice.

 

[Junus2012]

No dear t4_V I am not afraid

But I want to learn how to see it from pole and zero analyses,

Otherwise in my graph, I can see clearly the first dominant pole and the first non dominant pole at the bend after the GBW

 

[t4_v]

OK. Thank you for your reply. Now, I understand your query. I'm not into pole-zero analysis in Cadence, but isn't it that way that you look on poles on the left side of Y-axis. There you have 2 poles. Exactly, what is expected from AC characteristic as you wrote:

Otherwise in my graph, I can see clearly the first dominant pole and the first non dominant pole at the bend after the GBW

 

[vivekroy]

Can you zoom in around the x=0 axis? Your x-axis is in the units of THz and the very high frequency poles and zeros you see are some parasitics and I wouldn't worry about it too much. I am curious to see the low frequency parts.

 

[Junus2012]

Dear friends,

Thank you very much for your reply,

The simulator is giving the results in T Hz even when I tell him maximum 50 M,

There is some setting which I am missing