An 8-nW Resistor-less Bandgap Reference Based on a Single-Branch Floating PTAT Voltage

This letter presents an ultra low-power resistor-less bandgap reference circuit, which is based on the topology of a single-branch floating proportional-to-absolute-temperature (PTAT) voltage. By using a cascode high impedance current bias technique, the single-branch PTAT voltage can be directly floating on the complementary-to-absolute-temperature (CTAT) voltage generated by the $V_{EB}$ of the bipolar transistor. Ultra low power consumption is realized by the simple topology in the proposed method, which only needs a few current branches. Fabricated in 0.13- $\mu \text{m}$ CMOS process, this letter generates a 1.252-V bandgap reference voltage. The total power consumption is 8.26 nW with a 1.4-V supply voltage. Without a resistor, this letter can achieve a small active area of 0.017 mm2. The average value of the temperature coefficient is 68 ppm/°C from −20 °C to 110 °C, and the line regulation is 0.019 %/V.