A power factor correction apparatus which uses Pulse Frequency Modulation to control an ACDC converter is disclosed. The cylinder is expandable from an initial diameter to a pre-determined final diameter, wherein an increase in the diameter of the stent results in a substantial decrease in the length of the stent. The amplitude of an amplified analog audio signal also can be reconstructed if necessary, thereby providing better sound quality with the same level of sound. Additionally, tunable reactive compensation is applied to the compensation components of the lossless combiner as a function of the multilevel voltage setting of the PAs. A final fuel injection amount TOUTi is determined, on a cylinder-by-cylinder basis, according to a first filtered value KACT_Fc or a second filtered value KACT_Fr such that the amplitude of the filtered value KACT_Fc or KACT_Fr converges to a predetermined value.