about the stability of an OTA

[spring1860]

hi
i designed an ota ,and the ac performance is shown below, What the problem is the phase curve ,it start from 180deg fall to -90deg but then it rise to 240deg at freg=GBW, (see label "B") , and i dont know whether it is stably or not ..

can someone say something about the stability of an ota !

 

[Alex_IC]

Can you show the testbench for the OTA stability simulation. Maybe there is error...

Also you can use transient to check stability

 

[electronrancher]

It looks like a high-frequency zero, for example when the input signal begins to couple directly across one stage.

So although the amplifier is not fast enough to amplify at this high frequency, the signal can be passed directly through just with the parasitic capacitance.

 

[spring1860]

Can you show the testbench for the OTA stability simulation. Maybe there is error...

Also you can use transient to check stability

Hi Alex_IC:
I just do an AC analysis, and calculate the phasemargin from the phase curve ,but the phase curve falls first and then rise, i dont know which point should i refer to ..
thanks.

 

[rajanarender_suram]

i think u have interchanged +ve and -ve terminals for simulation