| 摘要 |
<p>PURPOSE: A method for using a magnetoresistive sensor in a second harmonic detection mode for sensing weak magnetic field is provided to improve signal to noise ratio for a multi layer magnetoresistive sensor by using inherent characteristics of a giant magnetoresistance unit and a magnetic tunnel junction part enabling low power consumption as having low cost and high resolution. CONSTITUTION: An AC driving current(430) is applied to a driving strap(70) overlaying a magnetoresistive sensor(10) in order to move an operation spot of the magnetoresistive sensor to a low noise region, and an AC driving magnetic field(440) is generated in the magnetoresistive sensor by the AC driving current. When the measured magnetic field is overlapped with the AC driving magnetic field in the magnetoresistive sensor, a second harmonic component is extracted from the output of the magnetoresistive sensor, and the extracted magnetic field is proportional to the amplitude having a sign of the extracted second harmonic component. [Reference numerals] (150) Detection circuit; (200) Generator; (210) Frequency divider; (220) Band pass; (230) Phase sensitive detector; (420) Free layer easy magnetization axis; (70) Drive strap; (80) Offset strap; (AA) Free layer magnetization; (BB) Reference layer magnetization; (CC) Sensing voltage; (DD) Signed amplitude of second harmonic component; (EE) Reference signal(2f)</p> |
