A CMOS 3.4 mW 200 MHz continuous-time delta-sigma modulator with 61.5 dB dynamic range and 5 MHz bandwidth for ultrasound application

This paper presents a low power high speed continuous-time (CT) delta-sigma modulator (DSM) for ultrasound application. The modulator was designed for a portable ultrasound digital beamformer to digitize ultrasound signal centered at 3.5 MHz with a fractional bandwidth of 0.6. A CMOS 0.18 mum 3^rd-order low-pass DSM sampled at 200 MHz was implemented. A transconductor (G_m) with improved linearity was proposed in order to reduce the power dissipation by increasing its linear input range. Simulation shows that the DSM can achieve a dynamic range of 61.5 dB and consume only 3.4 mW power at 1.8 V supply voltage.