Calibration signals are distributed to the respective output signals of a plurality of antenna elements, thereby multiplexing the distributed calibration signals with the respective signals of the plurality of antenna elements. The pair of transistors are activated concurrent with the deactivation of the switching transistor. In one embodiment, two rows of stagnation point film cooling holes are used to form a four hole showerhead. The current sensing circuit further includes a second sensing circuit coupled to the high-side switch for measuring current flowing in a negative direction through the high-side switch.