A 59 pA/V and 62 nW Differential OTA with 0.35% THD for Biomedical Applications





Analog design, OTA, Gm reduction, OTA-C


This paper presents a novel differential pA/V Operational Transconductance Amplifier (OTA) topology. The circuit is suitable for the implementation of fully integrated operational transconductance amplifier-capacitance (OTA-C) filters with small feature size capacitors, suited for electrophysiological signal acquisition and conditioning. Unlike typical OTA-Cs, the proposed topology consists of transconductance reduction technique based on unbalanced output branches that
allow current subtraction thus enabling transconductances in the order of pA/V. The technique is demonstrated through the design of a 59pA/V transconductor, which is very suited for designing long-time-constant filters. This OTA-C achieved a worst-case 0.35% THD with just 61.7nW average power consumption, which allows its applicability to biomedical implants. Simulations were carried out with STMicroelectronics 0.13µm HCMOS9 node using Cadence’s IC design tools. We
employed the OTA in a design of a fourth-order bandpass filter with a narrow bandwidth of 12.5–21.8Hz. Similar results to the ideal transfer function, turn the proposed OTA ideal for biosensing-based applications.

Author Biographies

Rafael Sanchotene Silva, Federal University of Santa Catarina (UFSC) - Brazil

Rafael holds a degree in Computer Engineering from the Federal University of Santa Maria (2015). He worked as a trainee at Design House Santa Maria (SMDH) in the area of analog circuit design. Master's degree at the Federal University of Santa Catarina (UFSC), Electrical Engineer area with an emphasis on Circuits and Integrated Systems, developing research on the characterization of MOS transistors for ultra low power applications at Integrated Circuits Laboratory (LCI-UFSC). Currently, he is in progress with a doctorate in biomedical engineering (UFSC - IEB).

Luís Henrique Rodovalho, Federal University of Santa Catarina (UFSC) - Brazil

Graduation at Universidade Federal do Pará (2011) and master's at from Universidade Federal do Rio Grande do Sul (2016). Has experience in Microelectronics, focusing on Ultra Low Voltage Analog Circuits.

Jefferson Luiz Brum Marques, Federal University of Santa Catarina (UFSC) - Brazil

JEFFERSON LUIZ BRUM MARQUES obtained his degree in Electrical Engineering (UFSM-Brazil, 1986), Master in Sciences in Biomedical Engineering (UNICAMP-Brazil, 1989) and a PhD in Medical Physics & Clinical Engineering (University of Sheffield-United Kingdom, 1994). He worked as a Clinical Scientist at the Department of Medical Physics & Clinical Engineering, Faculty of Medicine, Sheffield University (1995-1997). He is currently a Professor in Biomedical Engineering at the Federal University of Santa Catarina in the Department of Electrical and Electronic Engineering and holds a Researcher Productivity Scholarship grade 1D of the National Council for Scientific and Technological Development (CNPq) in the area of Biomedical Engineering. He has published several articles in specialized journals and proceedings of events related to his area of activity and research. He has developed software, hardware, and other technical production items. He supervised 54 master's dissertations and co-supervised 6; supervised 10 and co-supervised 2 doctoral theses; in addition to having supervised undergraduate research work and 34 final year projects in the areas of Electrical and Electronic engineering. Currently, he is supervising 13 master dissertation and 6 doctoral thesis in the post-graduation courses in Electrical/Biomedical Engineering, Medical Sciences and Health Informatics. Between 1998 and 2020 he participated in several research projects having coordinated some of them. He works in the area of Biomedical Engineering, with emphasis on biomedical signal processing, mathematical modelling of biological phenomena, electronic and biomedical instrumentation, electrophysiology. In his professional activities, he interacted with several collaborators in co-authorship of scientific works. In his curriculum Lattes the most frequent terms in the contextualization of scientific, technological production are: diabetes mellitus, digital signal processing, electronic and biomedical instrumentation, hypoglycaemia, electrocardiogram, medical informatics, digital image processing, artificial intelligence, bio-electromagnetism, early diagnosis and biomarkers, ubiquitous health and healthcare 4.0, electrophysiological measurements, diabetic neuropathies, chronic disease management, heart rate variability, epilepsy and physiological measurements.

Cesar Ramos Rodrigues, Federal University of Santa Catarina (UFSC) - Brazil

Cesar Ramos Rodrigues received the B.Sc. degree in electric engineering from Federal University of Santa Maria(UFSM), Santa Maria, Brazil. The M.Sc. and the Ph.D. degrees in electronics were received from State University of Campinas (Unicamp), Brazil, in 1990, and 1993, respectively. He joined UFSM as a Teaching and Research Assistant in 1997, where he started the Microelectronics group (Gmicro). In 2013, he was a visiting researcher with the Graduate School of Biomedical Engineering at UNSW (Sydney, Australia). In 2016 he was a visiting researcher with the Campus Bio-medico di Roma (Rome, Italy). After that, he started to focus on integrated circuits and artificial intelligence techniques applied to biomedical engineering, and moved (2019) to University of Santa Catarina (UFSC), Florianpolis, Brazil. Presently he is a professor with the Institute of Biomedical Engineering (IEB) at UFSC.