A Performance Evaluation of Class-B Amplifiers for Driving Piezoelectric Transducers

Abstract

Piezoelectric transducers are used in high power ultrasound systems. These devices are excited by electrical powers supplied by amplifiers at the transducer’s resonant frequency. The transducers can have performance variations caused by external effects such as acoustic loading and mechanical pre-stressing, which promotes changes in the magnitude of the electrical impedance and resonance shiftings. These variations can result in harmful consequences for the amplifiers. The Butterworth-Van Dyke (BVD) equivalent circuit is used to represent piezoelectric transducers. Complementary circuits are connected to the transducers aiming to obtain a resultant resistive load on the amplifier output. However, variations in transducer characteristics must compromise the amplifier operation. In this work, we will analyze the behavior of class-B amplifiers that drive piezoelectric loads. The efficiency limits and power balance in the amplifiers will be evaluated from the variations that may occur in the transducers.