Analog front end for proximity sensing of tunneling current

A circuit comprising:

• an input that receives a current that increases as a tunneling current sensor approaches a media;
• a first amplifier operatively coupled to the input to convert the received current as a first voltage output, wherein the first voltage output increases with increases in the received current until a saturation threshold is attained for the first amplifier, wherein further increases in the received current beyond the saturation threshold are diverted from the input as an overflow current;
• a second amplifier operatively coupled to the input to convert the overflow current as a second voltage output if an overthrow threshold for the second amplifier is attained, wherein the second voltage output increases with increases in the overflow current as the tunneling current sensor continues to approach the media;
• and
• a combiner to merge the first voltage output of the first amplifier and the second voltage output of the second amplifier into a control voltage that is employed to control the fly height of a disk head that reads or writes to the media.

A circuit comprising:

• an input that receives a current that increases as a tunneling current sensor approaches a media;
• a high gain path operatively coupled to the input to convert the received current as a first voltage output, wherein the first voltage output increases with increases in the received current until a saturation threshold is attained for the high gain path, wherein further increases in the received current beyond the saturation threshold are diverted from the input as an overflow current;
• a low gain path operatively coupled to the input to convert the overflow current as a second voltage output if an overthrow threshold for the low gain path is attained, wherein the second voltage output increases with increases in the overflow current as the tunneling current sensor continues to approach the media;
• a combiner to merge the first voltage output of the high gain path and the second voltage output of the low gain path into a control voltage that is employed to control the fly height of a disk head that reads or writes to the media;
• and
• a controller that receives the control voltage from the combiner to control the fly height of a head that reads or writes to the media.