Increase the Linear Range of Amplifiers, Filters, or Others with MOS Transistors, by Means of Substrate Degeneration

Participants: Joel Gak, Matías Miguez, Alfredo Arnaud, Diego Costa
Duration: 03/2019 to date

Linearity or distortion are essential parameters to describe the performance of an analog circuit. In an ideally linear circuit or amplifier the response is expected to be proportional to the input with a constant independent of amplitude or frequency; To characterize how linear an amplifier is, for example, the linear range is sometimes used, the total harmonic distortion (THD), third harmonic distortion (HD3), or other figures of merit depending on the application. In real circuits there is distortion because semiconductors are naturally non-linear, and there are various techniques to mitigate this effect.

In this project it is proposed to explore the linearization of amplifiers, filters, or other analog circuits with MOS transistors, through the use of the substrate (bulk) of the transistor. It is a technique that has been investigated for relatively few years, and with various open problems to solve. The effect of linearization through the substrate in circuits with MOS transistors in all operating regions including linear zone, triode, saturation, and in strong, moderate and week inversion will be reviewed theoretically, through simulations, and with measurements on integrated circuits to be designed. New structures will be proposed to reduce distortion in circuits using this technique, studying the relationship with other non-idealities in circuits such as noise or offset.

Filters and amplifiers will be designed to demonstrate the impact of linearization through the substrate on the performance of real circuits. Emphasis will be placed on micro and nano power consumption applications for implantable medical devices, but the potential range of uses is vast including among many other circuits for RF and telecommunications, amplifiers analog audio and for sensors.

RISC-HV: RISC-V Processor in HV for Medical Applications

Participants: Matías Miguez, Alfredo Arnaud, Joel Gak, Denisse Hardy, Kenji Nakasone, Leonardo Agis, Alfonso Chacón, R. García-Ramíre
Duration: 01/2018 to 07/2020

This project proposes the design, manufacture, and characterization of a SoC (system on a chip) in HV technology, including a RISC-V type CPU for the first time optimized for micro-consumption and specifically for implantable medical applications. Specific peripherals will be included such as high voltage digitals E/S, voltage boosters, and a current stimulator circuit, all programmable, and verifying common reliability and safety parameters in devices in contact with the patient.

Flicker Noise Stationary Cycle in MOS Transistors

Participants: Alfredo Arnaud, Matías Miguez, Joel Gak, Rafael Puyol
Duration: 06/2013 to 12/2015

The flicker noise in MOS transistors, due to the random capture / emission of charges by localized states, called traps, in the oxide, is an important limitation in circuits such as RF links, amplifiers, sensors, or even memories. Because it allows to reduce noise to physical level in the device, in recent years the study of stationary-cycle flicker noise (RFC) has gained interest, the flicker noise for the case of a transistor that is biased or turned off periodically.

However, the problem is complex, and to date there is no simple analytical model for the power spectral density (PSD) of the RFC that fully explains the reported experimental measurements, and these are still limited. This project raises through numerical simulations and experimental work, help to understand the phenomena physicists behind the flicker noise in the cycle-stationary case. An integrated circuit will be manufactured with test transistors of various types, and very low noise integrated amplifier circuits of attached flickers, in order to measure the RFC in a wide range of operating regions of the MOS transistor. Existing analytical models will be used, and numerical simulations will be carried out under different physical hypotheses, in order to adjust the experimental results.

The ultimate goal is to help understand the phenomena involved in the cyclo-stationary flicker noise, and explain some characteristics of its PSD, especially the reappearance of the spectrum 1 / f at very low frequency.

Integrated Circuits for Medical Devices

Participants: Matías Miguez, Alfredo Arnaud, P. Julian
Project Number: ANII FMV2009-1-3176
Duration: 03/2011 to 06/2012

In the last few years there have been a great increase in the development of implantable medical devices for new therapies. These battery operated devices require minimum energy consumption that can only be provided by low power integrated circuits.

Most active implants require stable voltage references, which do not vary as the battery voltage decreases with usage. In this project a low power integrated voltage reference, apt to be included in medical devices will be designed, sent to be fabricated and measured.

An analysis on the advantages and disadvantages of including active current mirrors over the traditional ones on implantable medical devices will be undertaken. In particular, the increase of the common mode rejection ratio (CMRR) without an excessive increase of current consumption (though total area will be significantly increased) will be studied.

This work is part of a doctoral thesis in electrical engineering.

Integrated Circuit for Cardiac Sensing

Participants: Jose Lasa, Alfredo Arnaud, Matías Miguez
Project Number: ANII FMV2009-1-3224
Duration: 01/2011 to 01/2012

The first part of the project consists in designing a complete integrated amplifier for cardiac sensing, taking advantage of the HV-CMOS technologie and taking into consideration the needs of implantables devices, minimizing the energy consumption.

A second part of the project will be to design a group of filters-amplifiers, using the switched capacitors wich will play the roll of a second stage of amplification. This design will tend to minimize the power consumption and to reduce the problems of charge injection.

In addition a low power consumption ultra low offset comparator will be design in order to complete the entire system of cardiac sensing.

This work is part of a master thesis in electrical engineering.

Design and Characterization of Low Noise Integrated Amplifiers

Participants: Alfredo Arnaud, Guillermo Costa, Nicolás Gimenez, Joel Gak, José Lasa, Matías Miguez, Julio Suárez, Juan Osta.
Project Number: ANII FCE2007-592
Duration: 03/2009 to 09/2010

Noise is a fundamental limitation to the development of analog integrated circuits. The problem becomes crucial in the case of implantable medical devices, because of power consumption restrictions, normally in the order of a few microwatts or less. This project deals with the design and characterization, of integrated amplifiers with a reduced input noise, low power consumption of a few microwatts.

To maximize the capability to extend the research to real products, the circuits were fabricated in a HV technology, normally employed for the development of integrated circuits for implantable medical devices. Also the benefits of HV technology regarding noise, and safety of medical circuits was investigated. The characterization of amplifiers in the frequency span of biological signals, requires precise low noise measurements at low frequency; the project includes the acquisition of laboratory instruments for this purpose.

Novell low-noise architectures were developed, some results are reported in the following papers:


The work team thanks the ANII-FCE for supporting the project.

Seminars presented within the framework of the project:

Seminar 1: "Circuitos CMOS en Tecnología HV". About HV technology, costs, applications.

Seminar 2: "Amplificadores Integrados en Tecnología HV". About developed integrated amplifiers: for EEG, cardiac sensing.

Other documents:

Informe sobre el Laboratorio de medida de ruido a bajas frecuencias, y resultados de medida de un amplificador de Miller diseñado y fabricado.

Informe de diseño, circuito integrado de sensado cardíaco.

Informe de diseño, amplificador de precisión para la medición de señales de EEG.

Other Seminars

Seminar presented: "Fuente integrada de corriente programable, para dispositivos médicos".

Seminar presented: "Filtros conmutados (SCTF) aplicados en amplificadores con Autozero".