Abstract: A fluxgate excitation circuit comprises an excitation inductor having a resistance Rsat and an inductance Lsat. Vin is provided by a half bridge converter of MOSFET switches (S1, S2). The excitation inductor is driven so that it enters saturation at the transition as the excitation cycle passes from positive to negative. Thus, a high input rms current value of the excitation circuit can be achieved. Because the excitation inductor is saturated for part of the cycle it may be much smaller than heretofore and have a smaller power supply. Thus, the circuit finds application in small devices.