A 0.8-V, 55.1-dB DR, 100 Hz Low-Pass Filter with Low-Power PTAT for Bio-Medical Applications

Abstract

This paper presents a power efficient transconductor-capacitor ($G_m-C$) filter for front-end processing of bio-medical signals. A low voltage, low-power transconductor with improved output resistance is proposed. It offers a transconductance ($G_m$) of 5.85 nS while operating at a supply voltage ($V_{dd}$) of 0.8 V. Furthermore, a low-power Proportional to Absolute Temperature (PTAT) current reference circuit is designed to bias the transconductor and to make $G_m$ independent of temperature. It follows PTAT characteristics in the temperature range of −20${}^{\circ }$C to 70${}^{\circ }$C and is less sensitive to $V_{dd}$ variations. A second-order Butterworth low-pass filter (LPF) with a cutoff frequency of 100 Hz is implemented to validate the proposed transconductor and the PTAT circuit. The filter is designed in UMC 65 nm CMOS process and it takes an area of 0.065 mm${}^2$. While consuming a power of 47 nW, it offers a dynamic range (DR) of 55.1 dB. Figure-of-merit (FoM) of the filter is as low as $4.2\times {10}^{-13}$ J, which is found to be on par with the filters reported in the literature.

Keywords:

• Bulk-driven transistor
• Low-frequency filters
• Low voltage and low-power transconductor
• PTAT current

ACKNOWLEDGMENTS

The EDA tools used for this work are supported under SMDP project funded by MeitY, Government of India.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

G. Hanumantha Rao

G Hanumantha Rao was born in Guntur, India. He received BTech degree in electronics & communication from KL College of Engineering, India and MTech in VLSI systems from NIT Trichy, India. Since 2015, he is pursuing his PhD in National Institute of Technology Karnataka, Surathkal, India. His research interests include low voltage, low-frequency continuous-time filters. Corresponding author. Email: [email protected]

S. Rekha

S Rekha was born in Puttur, India. She received the BE degree in instrumentation technology from SJCE Mysore, India and MTech in Industrial Electronics from NITK (KREC) Surathkal, India. She obtained her PhD degree from the Department of Electronics & Communication Engineering, NITK Surathkal, India. Since 2007 she has been an assistant professor with the National Institute of Technology Karnataka, Surathkal, India. Her research interests include analog and digital VLSI design. Email: [email protected]