How to change phase margin or introduce a pole?

[kundahari]

Hi friends...I didnt have much knowledge in Stability analysis, I have phase margin around 35 deg. i would like to increase to 60 deg, I would like to introduce pole. how can i do?
Can anyone provide some documention for this?
thanks a lot

 

[AdvaRes]

Stability analysis

Hi,
In order to modify the phase margin you have to introduce some changes to your Filter by modifying the value of its Capacitances and Resistors. If you wanna introduce a pole increase the order of your filter.

You can see in detail these techniques in any book for PLL or filter design like Gadner's books.

 

[LvW]

Re: Stability analysis

Hi friends...I didnt have much knowledge in Stability analysis, I have phase margin around 35 deg. i would like to increase to 60 deg, I would like to introduce pole. how can i do?

Do you like to introduce the pole with the aim to increase the phase margin or because of other reasons ?
The simplest way to increase stability is to enhance the phase by introducing a zero (not a pole). For this purpose you can use an active or passive lead network (in control theory terms: PD-T1)

 

[A_U_J]

Stability analysis

Check out:
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**broken link removed**

 

[yschuang]

Re: Stability analysis

The link seems to be dead.

 

[share08]

Re: Stability analysis

if a ota is designed, you should add a left plane zero to increase the stability.(not a pole)

 

[Sadegh.j]

Re: Stability analysis

Hi

You can see the stability analysis techniques in Razavi or Gray meyer. The important point is to put the capacitor in a place where you can use the Miller effect as much as possible.

 

[Sudhir.K.A]

Stability analysis

Hi,

I guess even adding/moving a dominant pole at much lower frequency will increase phase margin.

If you are not constrained by the bandwidth requirement just identify the dominant pole location and move it to much lower frequency. This increase your phase margin at the cost of bandwidth.

 

[LvW]

Re: Stability analysis

Yes, this is the very well known "lag compensation" which costs bandwidth - opposite to the lead compensation as mentioned in my reply dated july 29th.