ADL5569 common mode stability

Hi Nicolas

I am sorry for my late response.

it looks like you are using an ideal power splitter from termG1 to ADL5569. this should be a Balun to get 0 and 180deg phase signals.

I used StabFact and also formula which you attached, and got identical results.

Please let me know how it work on your side.

Thanks,

Nao

Hi Nao,

With your schematic, you simulate the diff-diff ADL5569 response. In this configuration, the ADL5569 is stable.

A fully differential amplifier has 4 ports. The 4-port stability can be broken down in two, the diff-diff and com-com stability analysis.

My ADS schematic simulates the com-com ADL5569 response with ideal power splitters. 

In my application, ADL5569 is used as an active balun.

In this configuration common mode will be applied at the amplifier's input.

On the output side, you may have a purely differential load which means that the common mode is not terminated (100% reflection for the common mode).

Checking the com-com response is required to ensure that the amplifier does not oscillate under some load condition.

BR,

N.

Hi Guarana,

I tried to perform common to common simulation, and saw over 3 at K-factor. I have just swapped terminal and resistors for common mode simulation. this might be different results from what you saw in your simulation. I am not sure which one is correct one. You used the ideal splitter. I used the ideal balun and simulated in common mode. 

Thanks

Hi Guarana,

I tried to perform common to common simulation, and saw over 3 at K-factor. I have just swapped terminal and resistors for common mode simulation. this might be different results from what you saw in your simulation. I am not sure which one is correct one. You used the ideal splitter. I used the ideal balun and simulated in common mode. 

Thanks