A Novel Piezoelectric Hydrophone ASIC With Low Input Noise Floor

Due to the susceptibility of piezoelectric hydrophones to low-frequency noise when operating underwater, their detection accuracy and efficiency are often compromised. To address this issue, this article explores a low-noise piezoelectric hydrophone application-specific integrated circuit (ASIC) designed for low-frequency environments. The design primarily includes a time-multiplexed charge-sensitive amplifier (CSA) based on correlated double sampling (CDS), a double-Miller compensation three-stage amplifier (DMCTA), a time-multiplexed fully differential programmable gain amplifier (PGA) with a chopper (TMFDPC), a folded cascode op-amp with auxiliary gain (FCOAG), and a low-pass filter (LPF). The CSA, TMFDPC, and LPF are all designed based on CDS and achieve time-division multiplexing, significantly suppressing voltage fluctuations caused by time-discontinuity issues, thereby reducing the noise level of the circuit. The TMFDPC incorporates a chopper structure to suppress 1/f noise and input offset. The switch design mitigates clock feedthrough (CF) and channel charge injection (CCJ) effects. The DMCTA and FCOAG ensure the high-performance operation of the CSA and TMFDPC. The proposed analog front end (AFE) has been fabricated in a 0.18- $\mu $ m CMOS process with an area of 0.698 mm2 and operates under a 5-V power supply. Test results indicate that the transient characteristics align with theoretical research and simulation results, with a working frequency as low as 0.8 Hz. The input noise of the ASIC is $2.6~\mu $ Vrms.