Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits
Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits
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DOI：
10.5617/jeb.380
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发表时间：
2012-01
影响因子：
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通讯作者：
P. Bertemes-Filho;Volney C. Vincence;Marcio M. Santos;Ilson X. Zanatta
中科院分区：
文献类型：
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作者：
P. Bertemes-Filho;Volney C. Vincence;Marcio M. Santos;Ilson X. Zanatta
摘要多频电生物阻抗（MEB）作为一种非侵入性的组织表征技术已被广泛应用。大多数MEB系统使用宽带电流源注入电流和仪表放大器测量产生的电位差。要成为可行的电流源，就必须在很宽的频率范围内具有本质上高的输出阻抗。大多数当代MEB系统中的电流源都是基于Howland电路的。这项工作的目的是将镜像改进Howland电流源（MMHCS）与三种基于操作跨导放大器（OTA）的电压控制电流源（即a类，ab类和电流输送器）进行比较。结果表明，在1 MHz时，电流输送电路和基于ab类ota的电流源均比MMHCS电路具有更宽的输出电流频率响应，输出阻抗大226%。所提出的ab类OTA电路的功耗为4.6 mW，而当前输送机的功耗为1.6 mW。然而，在-0.5到+0.5 V的输入电压范围内，MMHCS电路的最大总谐波失真为0.5%。基于ota的电流源将被集成到半导体工艺中。该结果可能对细胞阻抗测量和非常低功率的生物阻抗应用有用。
Abstract Multifrequency Electrical Bioimpedance (MEB) has been widely used as a non-invasive technique for characterizing tissues. Most MEB systems use wideband current sources for injecting current and instrumentation amplifiers for measuring the resultant potential difference. To be viable current sources should have intrinsically high output impedance for a very wide frequency range. Most contemporary current sources in MEB systems are based on the Howland circuit. The objective of this work is to compare the Mirrored Modified Howland Current Source (MMHCS) with three Operational Transconductance Amplifier (OTA) based voltage controlled current sources (i.e., class-A, class-AB and current conveyor). The results show that both current conveyor and class-AB OTA-based current sources have a wider output current frequency response and an output impedance of 226% larger than the MMHCS circuit at 1 MHz. The presented class-AB OTA circuit has a power consumption of 4.6 mW whereas current conveyor consumed 1.6 mW. However, the MMHCS circuit had a maximum total harmonic distortion of 0.5% over the input voltage from -0.5 to +0.5 V. The OTA-based current sources are going to be integrated in a semiconductor process. The results might be useful for cell impedance measurements and for very low power bioimpedance applications.