LC tank full bridge control for large coil variations

In this paper, we present a switching technique for a CMOS integrated class-D amplifier. That technique, based on activating each transistor two times per period, allows increasing the power delivered to the coil without reducing the quality factor. The proposed solution has been simulated using a UMC 0.18 um technology. This technique is applied to a low frequency medical application. An integrated circuit supplied by a small battery must be capable of controlling the emission of three coils integrated in a pill, with similar values, at 125 KHz, to detect externally the position of the pill in the digestive system.