A Low-Power Variable Gain Amplifier Design with 70-DB Gain Range and 1.28-DB Gain Error for Ultrasound Imaging System

This work presents a Variable Gain Amplifier (VGA) design with low power consumption and dB-linear characteristic for the ultrasound (US) imaging system based on the cell-based topology. It compensates for the distance attenuation of the US echo signal by providing a variable gain that increases exponentially over time. By cascading several VGA building blocks, the gain range of the combined dB-linear VGA can be increased. Each VGA building block is designed by common source input MOS transistors working in the triode region to approximate an exponential function for high robustness and low power consumption. Designed in the 65 nm CMOS process, the presented VGA occupies 0.02 mm2 and can regulate a linear gain variation range in decibels of 70 dB with ±1.28 dB maximum gain error. Meanwhile, more than 80 MHz of −3 dB bandwidth can be realized within the gain range. The total power consumption of the combined VGA is 0.384 mW with a 1.2 V supply voltage, and the input-referred voltage noise density is 20 nV/√Hz.