Effects of the positive feedback loop in self biased bandgap reference circuits

In low voltage bandgap reference circuits, biasing the opamp with the bandgap current results in a positive feedback loop. In this article, analysis of the loop formation, loop equations and stability criteria are derived. It has been shown that, general design methods for nested feedback loops may shadow the underlying stability problems. With the derived criteria, such problems can be avoided and stability of the bandgap can be guaranteed.