A Low-Power Reference Current Circuit for Uhf Rfid Tags

A novel CMOS subthreshold current reference circuit with an output current of 65 nA is designed. In some cases, the designed Proportional to Absolute Temperature (PTAT) current temperature coefficient values deviate significantly from the positive temperature coefficient values, and the Complementary to Absolute Temperature (CTAT) current temperature coefficient values deviate significantly from the negative temperature coefficient values. This paper proposes a technique of subtracting large temperature coefficient currents and adding them with small temperature coefficients to realize the temperature compensation of the reference currents, and a common source and common gate current mirror structure is used to improve the power supply rejection ratio (PSRR). The proposed current reference is fabricated in a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.18 \mu ~\mathrm{m}$</tex> CMOS process. Measurements show a temperature coefficient of output current of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$129 \text{ppm} /{ }^{\circ} \mathrm{C}$</tex> over the range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-20^{\circ} \mathrm{C}$</tex> to 100° C, a power supply rejection ratio of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-160 ~\text{dB} {@} 10 \mathrm{k} \text{Hz}$</tex> with a 2 V supply, and a linearity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.6 \% / \mathrm{V}$</tex> over a supply voltage range of 1.2 V to 3.2 V. In addition, the power dissipation is 740 nW with an area of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$156 * 156 \mathbf{\mu m}^{\mathbf{2}}$</tex>. It is suitable for low-power applications.