Constant Current Drive for Resistive Sensors Based on Generalized Impedance Converter

A generalized impedance converter (GIC) is presented in this paper as a programmable current source. A study of its properties and limitations is shown. Its current efficiency is compared with that of Howland topologies, and it is improved in this paper. The contribution of the operational amplifier static offsets to the current source is obtained by presenting typical values of these parameters, and an equivalent circuit with its differential and common modes is presented. The calculated and experimental GIC input impedances are obtained, showing its bandwidth limitation and proposing the possibility of extending the input impedance frequency response without varying its low-frequency value. In this paper, the GIC is used to provide constant current to a series sensor loop and a magnetoresistive current sensor (Wheatstone bridge), which are located within the GIC itself. In both cases, the GIC works under the dc regime, unlike usual ac use.