A high accuracy voltage controlled current source for handheld bioimpedance measurement

In bioimpedance measurements, Beta-dispersion is an important working frequency range, from low frequencies kHz up to 1 MHz, since it includes the pathological states_ Along this relevant frequency range, getting a stable and safe injected current below than 0.5 rnA with load impedance changing from 5 Ω to 10 kΩ remains a challenge for the design of Voltage Controlled Current Source (VCCS)_ In this study, we suggest the Enhanced Howland circuit in dual configuration with a negative feedback using the high bandwidth amplifier AD8041 to reach higher accuracy at higher frequencies up to 1 MHz. According to experiments, this circuit configuration is capable to maintain approximately constant current amplitude within an accuracy of 0.54% at 1 MHz.