A Precision Current Source for Cellular Impedance Measurement

The article is devoted to the development of a broadband electric current source for the purposes of impedance study of cell cultures. The impedance methods for cell study were analysed. The problem of high (up to
$10 \mathbf{M}\boldsymbol{\Omega})$
resistance of electrodes for cell research was determined. An analysis of existing circuit solutions for the current source was carried out in order to select an amplitude value suitable for accuracy and in the frequency range of 0.1 Hz - 200 kHz. An improved Howland current pump circuit was chosen as a suitable solution. To confirm the characteristics, simulations were carried out in the Multisim environment in the frequency range of 0.1 Hz - 200 kHz. The results of the simulations showed that the improved Howland circuit, when using a buffer in the feedback circuit, has an error in setting the amplitude of the load current of 0.422%. Additional Monte-Carlo analysis showed that with the 0.05% tolerance of passive components values the error in setting the amplitude of the load current is 1.4%.