Power Efficiency Characterization with Various Gate Oxide Thicknesses in Class DE Amplifiers for HIFU Applications

Abstract

Skin and cancer cell treatments using high-intensity focused ultrasound (HIFU) have garnered considerable attention as a technology with fewer side effects. Hence, various schemes have been developed to operate ultrasound transducers with high efficiencies. Class DE power amplifiers operate in zero-voltage switching (ZVS) and zero-derivative switching (ZDS); therefore, high-efficiency operation is possible. However, during the CMOS process, a difference in efficiency arises depending on the gate oxide process, which has not yet been analyzed. In high-power devices, a thick oxide layer is primarily used to prevent breakdown. However, this can lead to a decrease in power efficiency. This study analyzes the overall power consumption for each oxide layer thickness during the AMS H35 CMOS process and compares its efficiency. The results confirm that an output power of approximately 1.8 W and a power efficiency of 94% can be obtained with just a relatively thin gate oxide thickness of approximately 10 nm. Furthermore, an additional power efficiency of approximately 3% can be obtained by reducing only the gate oxide thickness.