senddilu
Newbie level 6
Opamp stabilty
Hello ,
I have some doubt regarding, effect of loop gain control over stability of Opamp.
Normally if we take a correctly designed single ended opamp, it has a one dominant pole, and nondominant pole after unity gan frequeny and a right half zero at twice that non dominant pole.
we ll take two cases:
1)One with worst case feedback factor ie 1. That is our opamp is unity gan buffer. Now our loop transfer function or loop-gain ie G(s) should not have Dc gain very much. That is if G(s)= K(1-bS)/(1+aS)(1+bS), we should not keep on increasing our K which dc gain of our open loop Opamp.
Because if we take Routh criterion for K=infinite or very high value, our pole has moved to right half plane. That is our sytsem is unstable. So our Dc gain must be in limits.
Is my argument right?
2)Anothe case with feed bach factor of 1/2. Our openloop transfer function is
G(s)= K(1-bS)/2(1+aS)(1+bS) . This must be more stable than the previous case.
Is that right?
Please answer me these question. Please suggest about control of loop gain over stabily.
Hello ,
I have some doubt regarding, effect of loop gain control over stability of Opamp.
Normally if we take a correctly designed single ended opamp, it has a one dominant pole, and nondominant pole after unity gan frequeny and a right half zero at twice that non dominant pole.
we ll take two cases:
1)One with worst case feedback factor ie 1. That is our opamp is unity gan buffer. Now our loop transfer function or loop-gain ie G(s) should not have Dc gain very much. That is if G(s)= K(1-bS)/(1+aS)(1+bS), we should not keep on increasing our K which dc gain of our open loop Opamp.
Because if we take Routh criterion for K=infinite or very high value, our pole has moved to right half plane. That is our sytsem is unstable. So our Dc gain must be in limits.
Is my argument right?
2)Anothe case with feed bach factor of 1/2. Our openloop transfer function is
G(s)= K(1-bS)/2(1+aS)(1+bS) . This must be more stable than the previous case.
Is that right?
Please answer me these question. Please suggest about control of loop gain over stabily.