Chin Hsia

By Chin Hsia

This chapter describes the use of silicon-on-insulator (SOI) technology to develop balanced slew-rate pulse generators for medical ultrasound scanners, especially for multi-channel portable systems. Since ultrasonic transducers are usually composed of piezoelectric materials, most of which are capacitive, and the resonant frequency is usually in the order of tens of MHz, it is preferred to convert the high-frequency excited signals into high-voltage pulses to efficiently drive the transducers. In addition, the second harmonic leakage of the high-voltage pulse signal output by the pulse generator needs to be controlled such that the pulse generator can be applied to tissue harmonic imaging. Based on these considerations, the pulse generator architecture with balanced rising and falling edges proposed in this chapter is designed by synthesizing low-power, high-speed level shifters and a high-voltage H-bridge output stage to output high-voltage pulse signals with low harmonic distortion. The entire circuit integrates an 8-channel pulse generator, producing pulse signals >100 Vpp. The rise and fall times of the pulses are within 18.6 and 18.5 ns, respectively. The overall quiescent current is <60 uA (including the on-chip power supply). The output current drive capability is >2 A and the second harmonic distortion is as low as −40 dBc, indicating that the integrated pulse generator can be used in advanced, portable ultrasonic harmonic imaging systems.

Part of the book: Photoacoustic Imaging