How to test the GBW of CMFB

[vidivici.world]

Hi, I want to test the GBW of CMFB in this OTA, but don't know where to separate the circuit and give the input or test the output. Can anybody tell me please? Thanks a lot[/img]

 

[frankliner]

Input signal at vr2. break the loop at node 3. output node 4.

 

[vidivici.world]

Input signal at vr2. break the loop at node 3. output node 4.

NO, can't be that way, at least we should not break the feedback network composed of M5/Ra/M7/M4, besides vr2 is a reference voltage, maybe we should not replace it with input signal.

 

[ella1923]

break loop at node 3..supply 1vac on the other input of m7, measure GBW at node connecting the two resistors, Ra

 

[vidivici.world]

break loop at node 3..supply 1vac on the other input of m7, measure GBW at node connecting the two resistors, Ra

why not give the 1vac input at node 3 at the side of M7, after breaking at node 3?
It seems in this way, it can be a loop. Besides what if break at node 5 and give the input signal at gate of M7, measure GBW at drain of M3? Will that be equivalent to the way you mentioned above?

 

[BackerShu]

I don't think break at node 5 is resonable because the exact output of the CMFB is node2.

 

[vidivici.world]

I don't think break at node 5 is resonable because the exact output of the CMFB is node2.

But breaking at node2 is not so easy. And it is a loop, so breaking anywhere inside may be equivalent, just the output differs.