A Compact Ultrasound Low-Noise Amplifier with 40 dB Built-in Time-Gain Compensation

Abstract

This thesis presents the design of a low-noise amplifier (LNA) with integrated time-gain compensation (TGC) for ultrasound imaging applications. The primary objective is to develop a compact, power-efficient solution that compensates for signal attenuation in deep tissue imaging. Traditional LNA and TGC systems are bulky and power-hungry, but by integrating TGC directly into the LNA, this work optimizes both size and power consumption while maintaining high performance. The design addresses key challenges such as process, voltage, and temperature (PVT) variations, linearity, and noise performance. The LNA-TGC is designed using TSMC 0.18 μm CMOS technology and features a variable gain range of 40 dB, maintaining a constant unity gain bandwidth (UGBW) to prevent distortion. The feedback network, utilizing two back-to-back MOS transistors in the triode region, is configured to provide an exponentially increasing resistance to enable dynamic gain control. A replica biasing circuit is designed together with feedback network. To ensure low noise and high linearity, the architecture incorporates a four-stage variable gain amplifier with carefully designed feedback paths. A trimming method is explored to tune the gain error against mismatches. Simulation results show that the design meets its noise, gain, and power consumption targets, making it suitable for high-resolution 3D ultrasound probes, particularly in medical imaging applications where space and power are constrained.