A Pitch-Matched Low-Noise Analog Front-End With Accurate Continuous Time-Gain Compensation for High-Density Ultrasound Transducer Arrays

This article presents a compact analog front-end (AFE) circuit for ultrasound receivers with linear-in-dB continuous gain control for time-gain compensation (TGC). The AFE consists of two variable-gain stages, both of which employ a novel complementary current-steering network (CCSN) as the interpolator to realize continuously variable gain. The first stage is a trans-impedance amplifier (TIA) with a hardware-sharing inverter-based input stage to save power and area. The TIA's output couples capacitively to the second stage, which is a class-AB current amplifier (CA). The AFE is integrated into an application-specific integrated circuit (ASIC) in a 180-nm high-voltage BCD technology and assembled with a 100 mu m-pitch PZT transducer array of 8 x 8 elements. Both electrical and acoustic measurements show that the AFE achieves a linearin-dB gain error below +/- 0.4 dB within a 36-dB gain range, which is >2x better than the prior art. Per channel, the AFE occupies 0.025 mm(2) area, consumes 0.8 mW power, and achieves an input-referred noise density of 131 pA/root Hz.