Microelectronic design of femptoampere circuits for energy harvesting-powered sensors with application to the IoT.

Description

A smart city is an urban area that makes use of information and communication technologies (ICT) to improve the quality of urban services or reduce their costs. It is supported on a great number of electronic sensors interconnected through a big network, namely, the Internet of Things (IoT), which collects data and provides information to effectively manage resources and assets. Since sensors must be autonomous and available for long, the use of ultra low-power low-voltage devices is mandatory, independently of the powering source of energy (i.g. battery-less like)

The objective of this proposal is to design basic analog and digital circuits in CMOS technology which will be used to implement autonomous sensors powered by energy harvesting techniques. Since low supply voltage and current consumption become unavoidable constraints for this application, MOS transistors must necessarily work below their threshold voltage (weak inversion) while biased by currents of the order of femtoampere.

In the first part of the project the researcher will be engaged in deepening his knowledge on the MOS transistor working in the sub-threshold (weak inversion) region. This will subsequently facilitate the design and simulation of basic circuits, in particular: amplifiers, reference voltages / currents, current mirrors, transconductors, oscillators, filters, logic circuits, etc.

The second part of the work consists in preparing for fabrication a test chip containing one or more of the above basic building blocks using a nanometric CMOS technology, which gives access to the realization of high-performance circuits that can contest with the state of the art published in recent IEEE articles.

The targeted basic circuits will make part of a library and will be used in the future for more complete applications such as: sensors readout interfaces, energy harvesting-powered, DCDC converters, wearable electronics, wireless body sensor networks, etc.

Required skills:

-This project requires a researcher willing to deepen his knowledge on microelectronics and electronics applied to very low power and low voltage circuits.
-General knowledge on analog and digital electronics, particularly on the MOS transistor.
-Familiarity with electronic/microelectronic circuits simulation and CAD tools (SPICE, LTspice, Cadence).

Bibliography
[1] Bernabé Linares-Barranco and Teresa Serrano-Gotarredona, ‘’On the Design and Characterization of Femtoampere Current-Mode Circuits’’, IEEE JSSC, VOL. 38, N° 8, pp. 1353-1363, 2003
[2] Bender Machado and Márcio Cherem Schneider, ‘’On the Minimum Supply Voltage for MOSFET Oscillators’’, IEEE TCAS I regular papers, 2014
[3] R. J. M. Vullers, R. van Schaijk, H. J. Visser, J. Penders, and C. Van Hoof, “Energy Harvesting for Autonomous Wireless Sensor Networks,” IEEE Solid-State Circuits Mag., vol. 2, no. 2, pp. 29–38, Jun. 2010, doi: 10.1109/MSSC.2010.93666