Wideband Fully Differential Current Driver with Optimized Output Impedance for Bioimpedance Measurements

Abstract : This paper presents a wideband fully differential current driver architecture suitable for bioimpedance measurements. It uses an improved regulated cascode to enhance output impedance, enabling accurate measurements of transfer impedances at low and high frequencies. The current driver architecture maximizes the output voltage swing. An independent reference voltage is used in order to compensate the process variations of the output common mode voltage. The circuit was designed in 0.18µm CMOS AMS process, operating from 1.8V supply voltage. The silicon area is 0.26 mm 2. The current driver has a 67 MHz bandwidth and can provide a maximum output current of 600 µA peak to peak with a Total Harmonic Distortion (THD) below 0.3% at low frequencies increasing to 0.6% at 8 MHz. Due to the use of regulated cascodes in the output stage, the circuit achieves a 79MΩ output impedance at low frequencies decreasing to 324KΩ at 1MHz, with an output voltage swing of 0.95 V.
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Submitted on : Thursday, September 13, 2018 - 6:38:27 PM
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Achraf Lamlih, Philippe Freitas, Stéphane David-Grignot, Jérémie Salles, Vincent Kerzérho, et al.. Wideband Fully Differential Current Driver with Optimized Output Impedance for Bioimpedance Measurements. ISCAS: International Symposium on Circuits and Systems, May 2018, Florence, Italy. ⟨10.1109/ISCAS.2018.8351464⟩. ⟨lirmm-01874027⟩

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