Design of Howland current sources using differential evolution optimization

Howland circuits have been widely used in Electrical Bioimpedance Spectroscopy applications as reliable current sources. This paper presents an algorithm based on Differential Evolution for the automated design of Enhanced Howland Sources according to arbitrary design constraints while respecting the Howland ratio condition. Results showed that the algorithm can obtain solutions to commonly sought objectives, such as maximizing the output impedance at a given frequency, making it a versatile method to be employed in the design of sources with specific requirements. The mathematical modeling of the source output impedance and transconductance, considering a non-ideal operational amplifier, was validated against SPICE simulations, with results matching up to 10 MHz.