Dual-sense impedance-matched reader

A disk drive having a read system supported by an arm over a surface of a rotatable disk, the read system comprising:

• a read head;
• an interconnect having first and second inputs connected to opposite sides of the read head and having first and second outputs;
• and
• a preamplifier system operatively connected to the first and second outputs of the interconnect, the preamplifier system comprising:
• a voltage-sense preamplifier having first and second inputs connected respectively to the first and second outputs of the interconnect, and having first and second outputs;
• a current-sense preamplifier having first and second inputs connected respectively to the first and second outputs of the interconnect, and having first and second outputs;
• and
• a summing circuit connected to combine the outputs of the voltage-sense preamplifier and the current-sense preamplifier.

A preamplifier system for connection through an interconnect to a read head, the interconnect having first and second inputs connected to opposite sides of the read head, having first and second outputs and having a characteristic impedance, the preamplifier system comprising:

• a voltage-sense preamplifier having first and second inputs for connection respectively to the first and second outputs of the interconnect, having first and second outputs, having an input impedance, and having a gain;
• a current-sense preamplifier having first and second inputs for connection respectively to the first and second outputs of the interconnect, having first and second outputs, having an input impedance such that the input impedance of the voltage-sense preamplifier in parallel with the input impedance of the current-sense preamplifier is equal to the characteristic impedance of the interconnect, and having a gain equal to the gain of the voltage-sense preamplifier;
• and
• a summing circuit connected to combine the outputs of the voltage-sense preamplifier and the current-sense preamplifier.