LEICI   25638
INSTITUTO DE INVESTIGACIONES EN ELECTRONICA, CONTROL Y PROCESAMIENTO DE SEÑALES
Unidad Ejecutora - UE
capítulos de libros
Título:
The Biological Amplifier
Autor/es:
F. GUERRERO; E SPINELLI
Libro:
Further Understanding of the Human Machine
Editorial:
World Scientific
Referencias:
Año: 2017; p. 463 - 500
Resumen:
Chapter 12-THE BIOLOGICAL AMPLIFIEREnrique Spinelli and Federico N. GuerreroLike a spying glass, it magnifies tiny electrical bioevents12.0-AbstractBiopotentials are essential signals that are immersed in the body like underwater currents in an ionic ocean. Electrodes allow their detection by transducing these ionic phenomena into electrical signals, feasible to be processed by electronic circuits. Thus, we do not have direct access to biopotentials but through variable (and sometimes unpredictable) electrode-skin impedances. Because of this, when available as electrical signals, biopotentials become faint and vulnerable to noise and interference sources. One approach to bypass this problem is to use invasive techniques such as skin abrading or percutaneous needles insertion, which bring us closer to the electrical source, thus reducing the impedance. These solutions try to find out a solution compromising the patients´ comfort, instead of working on electronic design. It is a task for bioengineers to design bioamplifiers able to acquire high quality signals using non-invasive techniques while dealing with high electrode impedances. This chapter describes the characteristics of biomedical signals available at the electrodes, the influence of external interference sources, and the desired bioamplifiers´ features to deal with. Classic and current amplifier design and new tendencies are herein presented, showing circuits for both traditional wet electrodes and capacitive electrodes. The latter is an emerging technology that does not require electrolytes (gel, liquid or paste), which allow picking up biopotentials without any skin preparation, even through dielectric films or cotton clothes. A note should be made about the term bioamplifier itself. When analog electronics were the predominantly available tool, biopotential measurements were improved by enhancing the amplifier design. This remains true, but in a time when digital electronics and integrated systems are ever cheaper and more efficient, we think about the bioamplifier in connection with a broader class of devices which encompass the digital domain. In this chapter we will discuss biopotentialacquisition systems, because the characteristics of data converters and mixed-signal devices have become an integral part of a bioamplifier design.