Low power current sources for bioimpedance measurements: A comparison between Howland and integrated CMOS OTA circuits

Electrical Bioimpedance Analysis has been widely used as a non-invasive technique for characterizing tissues. Most systems use a wideband and a high precision instrumentation, specially the current source. The objective of this work is to compare the Howland circuit with three OTA-based floating voltage controlled current sources. The results show that both Current Conveyor and class-AB OTA have a wider output current frequency response and both output impedance is 226 % bigger than the Howland circuit at 1 MHz. The class-AB OTA circuit presents a power consumption of 4.6 mW whereas 1.6 mW for the Current Conveyor. The results might be useful for cell impedance measurements and for very low power bioimpedance applications.