da Silva Pablo Dutra, Filho Pedro Bertemes
Electrical Engineering Department, State University of Santa Catarina, Mexico, Brazil.
J Electr Bioimpedance. 2024 Oct 5;15(1):145-153. doi: 10.2478/joeb-2024-0017. eCollection 2024 Jan.
Bio-impedance Spectroscopy (BIS) is a technique that allows tissue analysis to diagnose a variety of diseases, such as medical imaging, cancer diagnosis, muscle fatigue detection, glucose measurement, and others under research. The development of CMOS integrated circuit front-ends for bioimpedance analysis is required by the increasing use of wearable devices in the healthcare field, as they offer key features for battery-powered wearable devices. These features include high miniaturization, low power consumption, and low voltage power supply. A key circuit in BIS systems is the current source, and one of the most common topology is the Enhanced Howland Current Source (EHCS). EHCS is also used when the current driver is driven by a pseudo-random signal like discrete interval binary sequences (DIBS), which, due to its broadband nature, requires high performance operational amplifiers. These facts lead to the need for a current source more compatible with DIBS signals, ultra-low power supply, standard CMOS integrated circuit, output current amplitude independent of input voltage amplitude, high output impedance, high load capability, high output voltage swing, and the possibility of tetra-polar BIS analysis, that is a pseudotetra-polar in the case of EHCS. The objective of this work is to evaluate the performance of the Switching CMOS Current Source (SCMOSCS) over EHCS using a Cole-skin model as a load using SPICE simulations (DC and AC sweeps and transient analysis). The SCMOSCS demonstrated an output impedance of more than 20 Ω, a ± 2.5 output voltage swing from a +3.3 V supply, a 275 current consumption, and a 10 Ω load capacity. These results contrast with the + 1.5 V output voltage swing, the 3 Ω load capacity, and the 4.9 current of the EHCS case.
生物阻抗谱（BIS）是一种能够进行组织分析以诊断多种疾病的技术，例如医学成像、癌症诊断、肌肉疲劳检测、血糖测量以及其他正在研究中的应用。随着可穿戴设备在医疗保健领域的使用日益增加，需要开发用于生物阻抗分析的CMOS集成电路前端，因为它们为电池供电的可穿戴设备提供了关键特性。这些特性包括高度小型化、低功耗和低电压电源。BIS系统中的一个关键电路是电流源，最常见的拓扑之一是增强型霍兰德电流源（EHCS）。当电流驱动器由诸如离散间隔二进制序列（DIBS）之类的伪随机信号驱动时，也会使用EHCS，由于其宽带特性，需要高性能运算放大器。这些事实导致需要一种与DIBS信号更兼容的电流源，具有超低电源、标准CMOS集成电路、输出电流幅度与输入电压幅度无关、高输出阻抗、高负载能力、高输出电压摆幅以及进行四极BIS分析的可能性，在EHCS的情况下即伪四极。这项工作的目的是使用科尔 - 皮肤模型作为负载，通过SPICE模拟（直流和交流扫描以及瞬态分析）来评估开关CMOS电流源（SCMOSCS）相对于EHCS的性能。SCMOSCS表现出超过20Ω的输出阻抗、从 +3.3V电源获得的±2.5输出电压摆幅、275的电流消耗以及10Ω的负载能力。这些结果与EHCS情况下的 +1.5V输出电压摆幅、3Ω负载能力和4.9的电流形成对比。
