A 90Vpp 720MHz GBW linear power amplifier for ultrasound imaging transmitters in BCD6-SOI

Transducer drivers for ultrasound imaging are required to have high output power and operation frequency into the MHz range. Furthermore, in harmonic imaging, a well-established method resulting in enhanced contrast, higher harmonic echoes (usually the second) of the fundamental transmitted frequency, either generated by reflection from micro-bubbles or on propagation, are selectively detected and used for imaging [1]. As a consequence, the second harmonic of the transmitted signal is suppressed as much as possible and the received signal is derived solely from the nonlinear behavior of the body. Pulsers are usually adopted having high efficiency, being simple and lending themselves to harmonic imaging for example by means of out-of-phase pulse transmission techniques [1]. Output signals with arbitrary shape allow better performances, enabling apodization profiles with high resolution, beams with low harmonic content and instantaneous changes in transmit energy between pulses [2]. However, the implementation of arbitrary waveform generators in commercial solutions is presently limited to high-end systems because of manufacturing costs, power dissipation and space constraints. To this extent, the availability of an adequate IC technology such as BCD, handling high dynamic range signals at high frequency and capable of multi-watt level driving, opens up to the investigation of integrated amplifier topologies [3]. Advantages in terms of EM interference reduction, reliability improvement, space and cost would derive. Achieving adequate gain-bandwidth products is nonetheless challenging considering the limited f_T of high voltage devices.