Current source dedicated for direct digital synthesizers: Application to the giant magneto-impedance (GMI) sensors

A new design of a High Frequency (HF) current source for GMI magnetic sensors is presented. In this design, a Direct Digital Synthesizer (DDS) is coupled to a current pump to form a voltage-controlled current source. This source is capable of supplying HF currents (with optional DC level) with constant amplitude for a reasonable range of GMI load impedances and for frequencies up to more than 10 MHz. The electronic schematic of the current pump is given. The impact of its use on the correction of the GMI sensor output in open-loop is illustrated through a comparison with a voltage-to-current converter based on the use of a traditional injection resistor.