High-power burst and chirp amplifier for MHz ultrasonics

Power ultrasound has become a core technology in diverse applications, including cleaning, welding, noninvasive surgery, and chemical processing. These applications involve nonlinear effects, e.g., cavitation, which requires driving the ultrasonic transducer with high instantaneous power. Suitable commercial power amplifiers are generally expensive and of large physical size. To address the high barrier of entry, we present an inexpensive and compact amplifier design capable of delivering 4.4 kW peak-power (peak-to-peak voltage: 1.3 kV into a 50 Ω load), with logic-level control of the output amplitude, frequency, and phase. We tested the amplifier in a high-intensity focused ultrasound application, featuring a focusing piezoelectric transducer operating at 4 MHz in water immersion. The amplifier is based on parallel MOSFETs in a single-ended topology that switches current through the primary side of a transformer. An efficiency of 74% was achieved with 100 W average power and 4.4 kW peak power into a 50 Ω load.