Junus2012
Advanced Member level 5
Hello Analog guys
I designed a current mirror OTA with a partial positive feedback, the circuit is like the one I attached from Gregorian book, Figure Nr. 3.41.
After I finished the design , I have simulated the circuit with and without the positive feedback as shown in the first and second image respectively.
Here I have a couple of questions,
1. I believe that the positive feedback degrade the Phase margin as you can see fro the both images , but I need an explanation on this circuit how is degrading. I am thinking that this positive feedback because it reduces the effective load transconductance, then the second pole becomes at lower frequency toward the dominant pole. is it right assumption ????
2. in Holberg book he said for stable op-amp, the second pole should be beyond the GBW, but I see that in both cases the second pole is before the GBW, isn't it, please could you tell me where it is exactly in both cases ???
3. This positive feedback supposed not not to alter the GBW, but from the images it did effect, whay ??
Thank you very nuch
I need your help in this post very badly
I designed a current mirror OTA with a partial positive feedback, the circuit is like the one I attached from Gregorian book, Figure Nr. 3.41.
After I finished the design , I have simulated the circuit with and without the positive feedback as shown in the first and second image respectively.
Here I have a couple of questions,
1. I believe that the positive feedback degrade the Phase margin as you can see fro the both images , but I need an explanation on this circuit how is degrading. I am thinking that this positive feedback because it reduces the effective load transconductance, then the second pole becomes at lower frequency toward the dominant pole. is it right assumption ????
2. in Holberg book he said for stable op-amp, the second pole should be beyond the GBW, but I see that in both cases the second pole is before the GBW, isn't it, please could you tell me where it is exactly in both cases ???
3. This positive feedback supposed not not to alter the GBW, but from the images it did effect, whay ??
Thank you very nuch
I need your help in this post very badly