A 20.5-nW Resistor-Less Bandgap Voltage Reference With Self-Biased Compensation for Process Variations

This brief proposes a resistor-less bandgap reference (BGR) based on a leakage-based proportional-to-absolute-temperature (PTAT) scheme. The effect of process variations on the current is mitigated by employing self-biased current-limiting MOS transistors. The bias voltages needed for approximating a large resistance can be obtained from a single branch by placing threshold-sampling transistors on top of the BGR output. The fabricated BGR in 0.18- $\mu \text{m}$ CMOS occupies an active area of 0.035 mm ² and consumes 20.5 nW, and it shows a standard deviation of 0.68% at untrimmed reference voltages.