A low-voltage CMOS bandgap reference

The CMOS bandgap voltage reference described here uses the bipolar substrate-transistor and the bipolar-like source-to-drain transfer characteristics of MOS transistors in weak inversion to implement a voltage source that is proportional to absolute temperature (PTAT). A first version of PTAT source is derived from a circuit described previously. A second version is based on a novel cell that can be stacked to obtain the desired voltage. Both versions operate down to 1.3 V with a current drain below 1 /spl mu/A. A stability of 3 mV over 100/spl deg/C has been obtained with a few nonadjusted samples. Experimental results suggest some possible improvements to extend this stability to every circuit.