Experimental Technology and Management

[Objective] MEMS piezoelectric hydrophones offer advantages such as small size, high sensitivity, and passive operation, making them valuable for underwater detection, marine science, and defense applications. However, the electrical signals they generate are extremely weak and easily affected by noise, requiring analog front-end preprocessing. Existing solutions primarily rely on discrete components or large instruments, resulting in large size, limited integration, and restricted applicability, which hinder the miniaturization and array-based development of hydrophone systems. Therefore, developing a high-performance, low-noise, dedicated analog front-end chip holds significant engineering value and strategic importance. [Methods] This study presents a low-noise, dedicated analog front-end chip for MEMS piezoelectric hydrophones fabricated using a 0.18 μm CMOS process. Powered by a ±2.5 V supply, the chip integrates key modules including a charge-sensitive amplifier(CSA), a programmable gain amplifier(PGA), a switched-capacitor low-pass filter(SC-LPF), and an automatic gain control(AGC) loop. The CSA employs a hybrid chopping stabilization and auto-zeroing scheme to effectively suppress low-frequency and folding noise while avoiding the input impedance degradation observed in conventional architectures. The PGA provides 64 gain settings through a capacitor array, and the SC-LPF offers 16 selectable cutoff frequencies, enhancing adaptability across application scenarios. The AGC, based on a digital feedback strategy, dynamically regulates gain through peak detection and hysteresis comparison to maintain optimal amplitude range. Additional on-chip modules, including a clock generator, reference source, and power-on reset circuit, ensure stable system operation. [Results] Post-layout simulation results show an equivalent input noise spectral density of 231 n V/√Hz at 1 Hz and 59n V/√Hz at 1 kHz, demonstrating excellent low-noise performance. The nonlinearity between input charge and output voltage remains below 1.26%, indicating high linearity. The power supply rejection ratio exceeds 105 dB at low frequencies, and the common-mode rejection ratio exceeds 95 dB across most process corners, confirming strong immunity to interference. Transient simulations verify that the AGC effectively adjusts gain in response to input amplitude variations. The total layout area is 1 147 × 762 μm, and compared with previously reported designs, the chip achieves superior noise performance, programmability, and integration. [Conclusions] This study introduces a high-precision, low-noise, programmable-gain-and-bandwidth integrated circuit for a front-end chip tailored for MEMS piezoelectric hydrophones. The incorporation of advanced noise-suppression techniques and a flexible architecture substantially enhances signal conditioning performance and application versatility. Simulation results confirm its advantages in noise, linearity, and interference rejection, meeting the stringent requirements of weak underwater signal detection. The proposed chip provides a practical pathway toward the miniaturization and array implementation of hydrophone systems. Future research will focus on further reducing power consumption and chip area to lower overall energy use while maintaining high-performance and minimizing device size, thereby supporting broader real-world deployment of array systems, enhancing array sensor detection accuracy, and strengthening applications in marine exploration, ecological monitoring, military reconnaissance, and related fields. Additionally, the adjustable-gain and bandwidth architecture proposed in this study establishes a foundation for flexible configuration and multifunctionality in future sensor systems, offering strong scalability and adaptability.