Low-Noise CMOS TGC Amplifier With Adaptive Gain Control for Ultrasound Imaging Receivers

A CMOS time-gain-compensation (TGC) amplifier is presented in this brief to accommodate large dynamic input signals and contribute low noise in ultrasound imaging receivers. From the system level, this brief addresses the necessity of performing gain control in balancing dynamic range and noise performance of a TGC amplifier. It then illustrates the noise effect on this type of amplifiers and points out the potential design tradeoffs. At the circuit level, by employing a current feedback topology, a new TGC amplifier is proposed to achieve low noise, variable gain, and relatively constant bandwidth. A design prototype was fabricated with a 130-nm CMOS process. The measurement results successfully demonstrate a TGC amplifier with a constant bandwidth of 10 MHz and a variable gain ranging from 13.8 to 36.3 dB. The equivalent input-referred noise is 7.41 nV/√Hz, and the maximum harmonic distortion is below 0.8%.