0.25V Nanowatt Circuits

TITLE: 0.25V Nanowatt Circuits

Advisors: Sameer R Sonkusale

Researcher: Luis Henrique, Michael Trakimas (Completed)

Abstract:

Most emerging ideas for sensing rely on energy harvested from the environment. Circuit level innovations are still needed to allow operations at very low voltages and low power consumption. Moreover, novel circuit architectures are needed for different sensor modalities. Questions exist whether we can achieve high gain amplification when power supplies drop considerably lower than what is allowed by the CMOS technology? For example, can one even implement an amplifier at supply voltages much lower than 0.5V?

Approach:

We have proposed a combination of bulk-driven input transistors and also transistors operating in weak inversion region to reach the aggressive goals of power supply of just 0.25V. Negative-resistance source degeneration has been proposed to improve the transconductance and gain-bandwidth product even at lower current consumption. Layout techniques with distributed transistor implementation has also been proposed for improved (higher) output impedance.

Results:

In the area of application specific sensing front ends, we have miniaturized the entire electrochemical potentiostat including built-in microelectrode arrays all on a single chip for the first time (IEEE Sensors Journal 2009). In another work, we implemented a high gain transimpedance amplifier for potentiostat applications with much lower input impedance using a modified wilson current mirror topology with feedback (IEEE Sensors Journal 2010). We have also broken the barrier of 0.5V for analog circuits and have demonstrated first ever high-gain amplifiers (> 60-dB) operating at just 0.25V (IEEE Trans. Cir. and Sys. I, 2014) Beyond amplifiers, we have demonstrated a first of its kind delta sigma modulator that is operating at just 0.25V (IEEE Trans. On VLSI Sys. 2014). There is also a strong body of work from the group prior to the research effort on 0.25V circuits, such as making filters and amplifiers operating in subthreshold regions, current mode ADCs etc. (Journal of Analog Integrated Circuits and Signal Processing 2009 and IEEE Sensors Journal 2009, ISCAS 2005).

PUBLICATIONS:

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