A Low Noise Capacitive Feedback Analog Front-end for CMUTs in Intra Vascular Ultrasound Imaging

In this paper, we present the capacitive feedback analog front-end for intra vascular ultrasound (IVUS) imaging as opposed to the conventional resistive feedback analog front-ends. In our proposed capacitive feedback architecture, floating input node of the amplifier is dynamically biased during the transmit mode of the CMUTs (Capacitive Micromachined Ultrasound Transducers). During the reception mode, the biased voltage at the floating input node of the amplifier is stored on the gate of input transistor of the amplifier. A high voltage pulser circuit with small output capacitance is integrated on-chip with the proposed low-noise capacitive feedback receiver. The proposed capacitive feedback analog front-end circuit is designed using the 0.35 μm high-voltage CMOS technology library of Austria Microsystems Corporation. Based on post-layout simulation results, we were able to achieve an overall noise figure of 0.6 dB with the proposed capacitive feedback analog front end for the amplification of signals generated by a 100×200 µm2 CMUT array element.