A permalloy current sensor

The design, fabrication and output characteristics of a thin film Permalloy magnetoresistive magnetic field sensor in a balanced bridge configuration are described. The bridge elements consist of two magnetostatically coupled Permalloy films (100 to 500 A°) separated by a thin film titanium spacer (100 to 1,000 A°). When this bridge is integrated with electrically isolated overlay conductors, the resulting device is ideally suited to sense currents in power supply applications over a 0 to 100 MHz frequency range with negligible dc offset. Devices with 35 mV peak outputs optimized to sense 50, 250 and 500 mA peak currents have been implemented and tested.