words, this op amp does not provide the direct cancelation mechanism of the five-transistor OTA. Figure 11 plots the bandgap core PSRR in the presence of the two-stage op amp. Complete Bandgap Reference As prescribed by Figure 2(b), we must attach equal resistors from nodes X and Y to the ground to change the nature of ID1 and ID2 from PTAT to temperature-independent quantities. This requires that ()/ around V17 T n 16= RR ln fied circuit as well as ||ID2 Resistors R2 and R3 31VnT = . and RR R623 1 be if . Figure 12 displays the modiversus T. are rounded up to 13 ,kX and the op amp is implemented as the two-stage topology of Figure 9. We note that ||ID2 changes by less than 0.4% across our temperature range of interest. In the next step, we copy ID2 and apply the result to R ,L forming the reference voltage, V .out According to (6), an output voltage of 0.5 V requires . RR/ 042 because the quantity L 2 . within the parenthesis is around 1.2 V. It follows that Plotted in Figure 13 is Vout though ID2 R .. versus T, L 55kX = exhibiting a variation of 40 mV. Why does Vout drift so much even is fairly constant? This error arises from the temperaturedependent