A Differential SPDT T/R Switch for PMUT Biomedical Ultrasound Systems

This paper presents a differential T/R SPDT switch, designed in a 0.18 µm HV BCD technology for PMUTbased biomedical ultrasound systems. It incorporates a bootstrapping technique to pass high-voltage pulses and a shunt branch for improved isolation. The differential T/R switch is designed to interface with bimorph electrodes although a singleended version can also interface with conventional PZT/CMUT transducers. Post-layout simulation results show that the switch circuit exhibits 64 Ω on-resistance and -62 dB off-isolation. A figure-of-merit is proposed to compare ultrasound T/R switches. To the best of the authors’ knowledge, this differential switch is the first of its kind being reported for PMUT biomedical ultrasound systems.