A Compact Variable Gain Amplifier With Continuous Time-Gain Compensation Using Systematic Predistorted Gain Control

Abstract

This brief presents a compact variable gain amplifier (VGA) with continuous time-gain compensation (TGC) for ultrasound imaging. The proposed VGA utilizes an open-loop topology and transconductance-subtraction load for compact implementation with sufficient gain range. To compensate for gain nonlinearity of VGA, this work proposes a systematic predistortion of gain-control signal to enhance an accuracy of TGC operation. The proposed VGA implemented in 180-nm CMOS process occupies 0.025 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and consumes 0.96 mW for the maximum gain condition with a supply voltage of 1.8 V. A real-time continuous TGC has been illustrated in measurement. The fabricated VGA achieves a gain range of 37 dB, a gain error below 1.4 dB, and an input referred noise of 8.6 nV/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\surd }$ </tex-math></inline-formula> Hz for the maximum gain condition.