A Single-Stage 37 dB-Linear Digitally-Controlled Variable Gain Amplifier for Ultrasound Medical Imaging

This paper presents a variable gain amplifier (VGA) for an analog front-end (AFE) of ultrasound medical imaging. This VGA has a closedloop topology and shows a 37-dB-linear characteristic with a single-stage amplifier. It consists of an op-amp, a non-binary-weighted capacitor array, and a gaincontrol block. This non-binary-weighted capacitor array reduces the required number of capacitors and the complexity of the gain-control block. The VGA has been fabricated in a 0.35-mm CMOS process. This work gives the largest gain range of 37 dB per stage, the largest P1 dB of 9.5 dBm at the 3.3-V among the recent VGA circuits available in the literature. The voltage gain is controlled in the range of [-10, 27] dB in a linear-in-dB scale with 16 steps by a 4-bit digital code. The VGA has a bandpass characteristic with a passband of [20 kHz, 8 MHz].