Design considerations in bandgap references over process variations

In this paper, simple expressions to compute the error in the reference voltage of a bandgap reference (BGR) circuit over process variations are developed. They are used to compare the performance of two popular BGR topologies, and it is shown that even though both of them achieve identical temperature compensation, one of them is more vulnerable to process variations. Further, it is shown that some errors can be reduced by decreasing the resistor ratio at the expense of increase in the area of the bipolar transistors.