Opamp unstable while designing BGR

[Chinmaye]

I am trying to design a BGR for which I have designed an op-amp. When I run stb analysis, I find that the loop is unstable. This may be due to the presence of both positive and negative feedback. How can this be rectified?

 

[LvW]

For stability the negative feedback factor must dominate.
By the way - what is the meaning of "BGR"?

 

[FvM]

BGR = band gap reference, like below circuit

Possible problems:
Wrong bias point in stb gain analysis
OP compensation actually inappropriate

 

[LvW]

Feedback factors depend, of course, on the resistor values.

 

[nitishn5]

In a BGR, there is going to be 2 loops.
The Positive Feedback Loop,
The Negative Feedback Loop.

When you run the stb analysis, ensure that you are breaking the right loop. (ie. inserting the voltage source at the right loop)
Also, at the steady state operating point, your positive feedback loop should have gain <1.

Now the negative feedback loop, can be unstable as you are observing. Stabilize it by using the standard compensation methods. (Miller/Dominant pole, etc)

 

[LvW]

In a BGR, there is going to be 2 loops.
The Positive Feedback Loop,
The Negative Feedback Loop.

When you run the stb analysis, ensure that you are breaking the right loop. (ie. inserting the voltage source at the right loop)
Also, at the steady state operating point, your positive feedback loop should have gain <1.

Now the negative feedback loop, can be unstable as you are observing. Stabilize it by using the standard compensation methods. (Miller/Dominant pole, etc)

Unfortunately, we do not know how the circuit looks like and how stability analysis was performed (one possible realization wa shown in post #3).
More than that, no parts values are given. This would be essential for analyzing stability.