Method and apparatus for measuring an output signal of a floating transducer

A circuit for measuring an output from a magnetic head comprising:

• a converter having a differential input for converting a voltage to a current;
• a coupler for coupling the output from the magnetic head that is not referenced to a fixed potential to the differential input;
• and
• a voltage forming device responsive to the current from the converter to produce a voltage for measurement referenced to a fixed potential.

A transducer measuring circuit comprising:

• an operational amplifier having a differential input and a single ended output;
• coupling means for coupling a signal from the transducer that is not referenced to a fixed potential to the differential input;
• converting means coupled to the amplifier output for converting a voltage at the single ended output to an output current;
• and
• means for feeding back a signal from the converting means to the differential input,
• wherein the single ended output is referenced to a fixed potential and the coupling means is substantially isolated from the fixed potential.

A magneto-resistive head voltage measuring circuit comprising:

• a CMOS operational amplifier having a differential input stage coupled to a single ended output stage;
• a CMOS coupler for coupling a voltage output from the magneto-resistive head that is not referenced to a fixed potential to the differential input stage;
• a CMOS voltage to current converter coupled to the single ended amplifier output for converting a voltage at the single ended output to an output current;
• and
• a CMOS feedback element for coupling a portion of the converter output current to the input of the differential input stage,
• wherein the single ended output stage includes an output that is referenced to a fixed voltage line and the coupler for coupling the voltage from the magneto-resistive head to the differential input stage is isolated from the fixed voltage line.

In a magneto-resistive head measuring circuit including an operational amplifier having a differential input and a single ended output referenced to a fixed potential, a method of measuring an output voltage of the magneto-resistive head comprising the steps of:

• coupling the output voltage of the magneto-resistive head that is not referenced to a fixed potential to the differential input;
• converting an output voltage of the single ended stage to an output current;
• and
• feeding back the output current to the differential input,
• wherein the coupling of the magneto-resistive head output voltage is isolated from the fixed potential.