Inverter-based Low-power, low-noise SC-VGA and 8 channel pipelined S/H analog beamformer for ultrasound imaging probes

This paper presents an inverter-based low-power low-noise switched-capacitor variable gain amplifier (SC-VGA), and an 8-channel sample-and-hold (S/H) analog beamformer (ABF) for 2-6 MHz second harmonic cardiac ultrasound imaging probes. The sampling frequency is 40 MHz in both the SC-VGA and the ABF. The SC-VGA has 8-bit gain control and achieves the dB-in-linear gain range from -14 dB to 32 dB. To suppress the second harmonic distortion (HD2), the SC-VGA completes the single-ended to differential conversion. By using a 2D piezoelectric transducer (PZT) model as the signal source, the SC-VGA performs the signal-to-noise ratio (SNR) of 45.4 dB, HD2 of -50 dB at the output swing of 820 mVpp, and power consumption of 214 μW at a supply voltage of 0.9 V. An 8-channel pipelined S/H ABF based on the SC analog memory following the SC-VGAs can improve the SNR to 54 dB and the HD2 to -54.3 dB. Each channel in the ABF consists of eight SC analog memories, and the total delay is up to 200 ns with the resolution of 25 ns. The summation amplifier in the ABF is an inverter-based differential SC amplifier, and its power consumption is 228 μW at a 0.9 V supply voltage. The simulation is based on 0.18 μm CMOS technology.