Patent ID: 9625538
Date: 2017-04-18
CPC Classifications: G01R

Claim:
1. A circuit for sensing an external magnetic field, comprising: a first voltage source for providing a power voltage; a first magnetic sensor for providing a reference current; a first conductive wire over the first magnetic sensor, to apply a set current and thereby set the first magnetic sensor to a reference state during a sensing period for the external magnetic field, wherein the external magnetic field is also applied to the first magnetic sensor; a second magnetic sensor for sensing the external magnetic field in the sensing period, a conductivity of the second magnetic sensor varying in response to the external magnetic field; a second conductive wire over the second magnetic sensor, to reset the second magnetic sensor before entering the sensing period; a bias voltage unit connected to the first magnetic sensor and the second magnetic sensor for providing a bias voltage to the first magnetic sensor and the second magnetic sensor; a clamp voltage current mirror unit for generating the reference current for the first magnetic sensor and mirroring the reference current to the second magnetic sensor; and a signal transfer amplifying unit for generating an output voltage and an additional current to compensate the change in the conductivity of the second magnetic sensor.