Abstract
The passive electrical properties of biological tissue have been studied since the 1920s, and with time, the use of Electrical Bioimpedance (EBI) in medicine has successfully spread (Schwan, 1999). Since the electrical properties of tissue are frequency-dependent (Schwan, 1957), observations of the bioimpedance spectrum have created the discipline of Electrical Impedance Spectroscopy (EIS), a discipline that has experienced a development closely related to the progress of electronic instrumentation and the dissemination of EBI technology through medicine.
Key Terms in this Chapter
Electrical Bioimpedance: The physical magnitude that indicates the total impediment that a biomaterial offers to the flow of free electrical charges and the orientation of bounded electrical charges towards an existing electrical field.
Negative Impedance Converter: Type of electric circuit that can generate any impedance between two points—capacitances or inductances.
Transconductance: A contraction of transfer conductance, the relation between the voltage at the input of an electric system and the current at the output. It is denoted by gm and measured in Siemens units.
Differential Amplifier: An amplifier whose output depends on the difference between two inputs through a gain (differential gain), and residually on the mean voltage between both inputs.
Parasitic Capacitance: A capacitance usually defined between a node and ground, due to wires, tracks, pads, and p-n junctions in the signal path.
Current Source: A two-terminal analog electronic building block which generates an electrical signal with constant current amplitude independently of the load connected at the terminals.
Operational Amplifier: Differential amplifier with a high open-loop gain which allows the implementation of accurate circuits by using voltage feedback.