Protection Circuit Design for Ultrasound Transducers

In ultrasound systems, a protection circuit must be used to protect the receiver electronics from the high-voltage pulses generated by the transmitter and to minimize the signal loss and distortion of the low-voltage echoes generated by the transducer. Especially for certain ultrasound applications, such as intravascular ultrasound, particle manipulation, and cell stimulation, proper performance of the ultrasound transducers is desirable due to their low sensitivity. As the operating frequency of the ultrasound transducer increases, the size of the transducer decreases, increasing the amplitude of the transmitted signals to achieve proper acoustic performance. In such environments, a protection circuit can be used to protect the receiver electronics in ultrasound systems. To design suitable protection circuits, transistors, resistors, capacitors, and inductors are used, and the parameters of insertion loss, noise, total harmonic distortion, and recovery time of the protection circuits must be carefully considered. Various approaches have been developed to protect circuits such as transmission lines, transformers, bridge diodes, and metal-oxide-semiconductor field-effect transistor devices. Certain protection circuits are beneficial for impedance matching and area reduction. Other protection circuits have been designed to increase bandwidth, reduce insertion loss, or improve the signal-to-noise ratio for different ultrasound applications. Therefore, this review article may be useful for academic ultrasound researchers or circuit designers in selecting appropriate protection circuit types for specific ultrasound transducer applications.