A 65.9-dB PSRR, Compact LNA Array for Correlated Noise Compression in High-Channel-Count Pitch-Matched Ultrasound ASICs

In high-channel-count matrix ultrasound transducers, correlated noise between channels could introduce the “white flashlight” artifact in the reconstructed ultrasound image. Such artifact usually becomes more severe when the matrix ultrasound transducer is closely integrated with pitch-matched application-specific integrated circuits (ASICs), where interference from electrical power supplies dominates the correlated noise. To tackle this problem, this article presents a PSRR-enhanced nine-channel ultrasound low-noise-amplifier (LNA) array that employs a shared low-dropout regulator (LDO) to compress the impact of the correlated noise from power supply. This work utilizes inverter-based LNA with split-capacitor and dynamic biasing techniques to achieve small area ( $110\times52.7~\mu $ m), low input referred noise (5.34 nV/ $\sqrt {\mathbf {Hz}} $ ) and low power consumption ( $50~\mu $ A) simultaneously. To enhance the power supply rejection ratio (PSRR) performance while maintaining high area- and power-efficiency, the LNA array incorporates a compact ( $50\times70~\mu $ m) local regulator based on a flipped-voltage-follower (FVF) with dynamically biased current-mode feed-forward ripple cancellation (FFRC). Fabricated in a 0.18 $\mu $ m BCD process, the proposed LNA array, including bias and local regulator, occupies only 0.0068 mm2 per channel and consumes an average power of 0.134 mW. Each LNA achieves a PSRR of 65.9 dB at 5 MHz, which is 20 dB better than the state of the art.