Predicting the effects of error sources in bandgap reference circuits and evaluating their design implications

Errors that arise from tolerance variations and mismatches between devices severely degrade the performance of bandgap reference circuits, which are essential building blocks to all high-performance systems. All these error sources have been analyzed (and verified through SPICE) and their design implications have been addressed. It has been found that resistor tolerance aid current-mirror mismatch are the dominant sources of error in bandgap reference-type circuits. Further, it has been found that resistor mismatch, transistor mismatch, and current-mirror mismatch errors have a PTAT variation, while resistor tolerance error has a CTAT dependence - both PTAT and CTAT errors are eliminated by trimming the PTAT terminating resistor in a bandgap circuit, only at room temperature. Resistor TC errors cannot be trimmed out and hence resistors must therefore be carefully selected and designed.