A 3.7-nW 248-ppm/°C Subthreshold Self-Biased CMOS Current Reference

A modified self-biased <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-multiplier-based current reference (CR) circuit is proposed for ultralow-power Internet of Things (IoT) application and is realized without any resistors, bipolar junction transistors (BJTs), or operational amplifiers (OPAs). The proposed CR circuit directly generates the reference current from a modified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-multiplier, which is biased by a stacked diode-connected MOS transistor (SDMT)-based compensated through a complementary-to-absolute temperature (CTAT) voltage. The proposed CR is implemented in a standard 0.18-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS process with an active area of 0.0069 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and almost all transistors operate in the subthreshold region. Measurement results show that the temperature coefficient (TC) of the CR is 248 ppm/°C in a temperature range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40~^{\circ }$ </tex-math></inline-formula>C to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$125~^{\circ }$ </tex-math></inline-formula>C. The proposed CR exhibits a line sensitivity (LS) of 0.33%/V within the supply voltage range of 0.8–1.4 V. The output of the CR at room temperature (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~^{\circ }$ </tex-math></inline-formula>C) is 1.84 nA with a power consumption of 3.7 nW.