[SOLVED] GBW measurement from closed loop buffer connection

[Junus2012]

I am sorry to make this discussion long, but may you forgive me, I am dealing in many years with the GBW product as constant or approximate constant for any compensated Op-amp, and I just came to know now that is not true, then I need also a couple of years to believe this new fact

I have also commented something in last post, if you could please answer me

Thank you very much

 

[FvM]

I think, most questions in your previous post, except for the CFB point, have been already adressed in previous contributions by LvW and myself.

Have the second pole slightly before or behind the unity gain frequency doesn't make a big difference. Of course, with 45° or less phase margin you get serious ringing and large gain peaking. But the constant GWBP concept is based on single pole characteristic and near to 90° phase margin.

The concept is helpful and gives fair bandwidth estimations if you don't apply it to gains of 1 or 2. If you review datasheet sof highspeed OPs, you'll probably find a unity gain bandwidth specified along with the GWB. See e.g. TI OPA354, GWB 100 MHz, UGBW 250 MHz.

 

[Junus2012]

Thank you very much guys

Thank you in advance