Patent ID: 7375912

Claim:
Fly height controller circuitry for controlling the power applied to a resistive heater in a disk drive head, comprising: an error amplifier, having a first input receiving a desired power level signal, having a second input receiving a feedback power signal, and having an output at which the error amplifier presents an error signal responsive to a difference between the signals at its first and second inputs; a first variable current source, having a control input coupled to the output of the error amplifier, for sourcing an output current into the resistive heater; a second variable current source, having an input coupled to the output of the error amplifier, for generating a feedback heater current signal based on an output current scaled relative to the output current sourced by the first current source; and a multiplier, for generating the feedback power signal corresponding to a product of the feedback heater current signal with a feedback voltage corresponding to a voltage at the resistive heater.