Optimum area allocation for minimum mismatch [IC device area optimization]

Circuit performance parameters such as offsets or common mode rejection ratio are limited by the matching of the individual elements. A technique is presented that allows one to determine the minimum total active area required to meet a specification limited by mismatch. Furthermore, the technique can be used to determine the optimum allocation of the active area amongst an arbitrary number of individual devices. A closed form optimum solution is presented for a folded cascode amplifier, and the technique is used to reduce the active area of an existing bandgap reference by 44% while maintaining an output voltage standard deviation of 2 mV.