Method and apparatus for biasing a magneto-resistive head

An apparatus for biasing a magneto-resistive head, comprising:

• a) an adjustable current source interconnected with a first terminal of a magneto-resistive head;
• b) first control means for detecting a voltage at the first terminal of the head and for adjusting a current provided by said adjustable current source whereby the voltage at the first terminal of the head is substantially maintained at a first predetermined voltage, said first control means comprising a first op-amp for generating a signal representative of the difference between the voltage at the first terminal of the head and the first predetermined voltage, said first op-amp having a non-inverting input interconnected with a first voltage source, an inverting input interconnected with the first terminal of the head, and an output interconnected with a control terminal of said adjustable current source, said first voltage source providing a voltage equal to the first predetermined voltage;
• c) an adjustable current sink interconnected with a second terminal of the head;
• and
• d) second control means for detecting a voltage at the second terminal of the head and for adjusting a current provided by said current sink whereby the voltage at the second terminal of the head is substantially maintained at a second predetermined voltage.

A magneto-resistive head apparatus, comprising:

• a) a magneto-resistive head having first and second terminals;
• b) a first biasing section, interconnected in series with said magneto-resistive head, for substantially maintaining said first terminal of said head at a first fixed predetermined voltage;
• and
• c) a second biasing section, interconnected in series with said magneto-resistive head and said first biasing section, for substantially maintaining said second fixed terminal of said head at a second predetermined voltage;
• wherein, in operation, said magneto-resistive head is biased at a voltage substantially equal to the difference between the first and second predetermined voltages.

A method for maintaining a predetermined DC potential across a magneto-resistive head, comprising the steps of:

• a) comparing a first operating voltage, at a first terminal of a magneto-resistive head, with a first fixed reference voltage;
• b) adjusting a current provided by an adjustable current source interconnected with a first terminal of the head until the first operating voltage is substantially equal to the first fixed reference voltage, wherein a predetermined DC potential across the head is established substantially equal to the difference between the first and second reference voltages;
• c) comparing a second operating voltage, at a second terminal of the head, with a second fixed reference voltage;
• and
• d) adjusting a current provided by an adjustable current sink interconnected with a second terminal of the head until the second operating voltage is substantially equal to the second fixed reference voltage.