TINA/Spice/LM2904: TINA/Spice/LM2904 simulation result (design margin)

 

 

Hello Hsu,

Can you please try to reattach the image of your circuit?

For some reason, we cannot see it on our side. Perhaps there was an issue in the attachment.

Thanks,
Daniel

Hi Hsu,

As Daniel noted, if you could reattach your images, that would be helpful.

A general comment on the current LM2904 model, it is quite inaccurate and old. We have a new model which will be available online in the next week or so.

Addressing a few of your comments:

* 30-degree phase margin is stable? But not in mass production.
* It is better to keep phase margin > 45- degree as a rule of thumb.
[TI] You are correct that 30 degrees of phase margin is not stable and that it is better to keep phase margin more than 45 degrees. To account for process, temperature, and variation, we actually prefer 60 degrees.

* In above circuit, by adding a C1 220pF as capacitive load at the op amp output, there is a gain peaking about 7-dB meaning phase margin left about 20~30-degree. Could I say this circuit (single case) is stable?
[TI] No, as you noted, we typically like more than 45 degrees for stability.

Thanks,
Paul

Hi, Paul and Daniel :

Thankx so much for your kindly feedback.

and let me re-attch the simulaiton result for your reference.

If you have any further comments, just let me know.

thankx again.

CD

Hello Paul,

Thank you for help!

May I know roughly time frame that we can have revised LM2904 spice model?

Thank you!

Regards,

Ting

Hello Paul,

Thank you for the great works!

Regards,
Ting