Stability Analysis for Howland Current Source for Bioimpedance Measurement

Howland current source is a promising circuit for bioimpedance measurement systems used in many medical applications. Although its simplicity and performance, it requires stability analysis due to its dependence on operational amplifier characteristics and resistor configuration. The trade-off between high output impedance and low output current, oscillations at high frequencies up to 1 MHz remains a challenge to ensure a stable Howland current source. Several cases studies of compensation capacitors in different positions in the circuit are analysed in order to guarantee at the same time a high output impedance and low output current oscillations at low and high frequencies.