Patent ID: 7961418

Claim:
A resistivity sense bias circuit for use with a magnetoresistive read head, comprising: a first transistor with a first emitter coupled to a first terminal of the magnetoresistive read head; a second transistor with a second emitter coupled to a second terminal of the magnetoresistive read head; a bias source connected between the base of the first transistor and the base of the second transistor, whereby the bias source establishes a bias current through the magnetoresistive read head; a first resistor connected to a collector of the first transistor; a second resistor connected to a collector of the second transistor; a first current source connected to the first emitter and the first terminal of the magnetoresistive read head to provide a first current; a second current source connected to the second emitter and the second terminal of the magnetoresistive read head to provide a second current; a first operational amplifier connected to the first emitter and the second emitter to output a signal based on a difference between a voltage potential at the first emitter and a voltage potential at a second emitter; and wherein a total current applied to the magnetoresistive read head is equal to the difference between the first current and the second current plus the bias current, further comprising a resistor having a fourth current connected to an output of the first operational amplifier.