jimito13
Advanced Member level 1
Hello,
I am trying to calculate the loop gain and phase for my design after inserting the common mode feedback loop of the main opamp.This design consists of a fully diff folded cascode opamp with gain boosters.
For measuring the above things i run stb analysis with the iprobe component but the result does not seem reasonable...a flat line with some negative kdB's gain and something similar (absolutely flat line at 180deg) for the phase plot.I tried to put the iprobe component in different places (inverting input of the opamp,inverting output of the opamp,cut the loop somewhere else and put it there) but the result is the same.Where is the right place to insert the iprobe for correct measurements??
And a final question.When running stb analysis,should i or slouldn't i inject ac diff signal at the inputs of the opamp?I suppose that answer is yes since stb seems to run ac analysis at the background but i am not certain.
Thanks in advance for any helpful answer.
I am trying to calculate the loop gain and phase for my design after inserting the common mode feedback loop of the main opamp.This design consists of a fully diff folded cascode opamp with gain boosters.
For measuring the above things i run stb analysis with the iprobe component but the result does not seem reasonable...a flat line with some negative kdB's gain and something similar (absolutely flat line at 180deg) for the phase plot.I tried to put the iprobe component in different places (inverting input of the opamp,inverting output of the opamp,cut the loop somewhere else and put it there) but the result is the same.Where is the right place to insert the iprobe for correct measurements??
And a final question.When running stb analysis,should i or slouldn't i inject ac diff signal at the inputs of the opamp?I suppose that answer is yes since stb seems to run ac analysis at the background but i am not certain.
Thanks in advance for any helpful answer.