Design and Comparison of the Switching Mode Power Amlifiers for Ultrasonic Frequencies

This thesis presents detailed analysis and comparison of different power amplifiers(PAs) for ultrasound frequencies.This thesis focus mainly on switching mode PAs because of their high efficiencies. The transistor is mainly used as a switch to avoid concurrent voltage and current on the switch, which reduces power dissipation. Theoretically the efficiency can approach 100%. Realisitcally, the efficiency can not reach 100%. The main reasons are non-ideal effects in the active and passive components. The transistor is a non-ideal switch, and thus power will be dissipated by the switch. The main cause of power consumption is series resistance and self-resonant frequency of the inductors. This thesis analyzes the drain efficiency of the switching mode PAs for ultrasound frequencies and compares the output power, cost and area used by the PAs. This research designed and compared different switching mode PAs. The power supply of these circuits are 5V to 10V. Fast fourier transform of time-domain captured signals were used to calculate the dc power and output power at the fundamental frequency. Finally, the drain efficiency can be calculated and the source of power consumption can be analyzed. The fundamental frequency of these circuits are 1MHz. The drain efficiency of Class-D PAs are the highest. Though Class-D PAs have the best drain efficiency, its output power is the lowest. Class-F-1 and Class-F PAs have larger output power than other types of PAs. Class-E PAs have the best overall performance considering between the drain efficiency and output power.