An apparatus (1000) and method for sensing load current of an envelope tracking (ET) modulator (1150) enables load impedance of a power amplifier (130) to be measured. Impairments associated with the load impedance characteristic can be suppressed by calibration and pre-distortion instead of by feedback. The ET modulator (1150) provides a switching regulator that can be reconfigured as a linear regulator for the purpose of sensing the load current. This allows the ET modulator (1150) to be operated open-loop, thereby eliminating the power consumption overhead resulting from utilization of a loop filter and error amplifier and achieving a higher overall efficiency.