Design and Comparison of Low-Noise CMOS Pre-Amplifiers for Piezoelectric Sensors in SONAR Applications

This paper presents the design of a custom low-noise CMOS operational amplifier and its application in different preamplifier topologies for SONAR systems. In underwater acoustics, minimizing the input-referred noise of front-end electronics is essential to ensure that weak signals are not masked by circuit noise. A two-stage operational amplifier, implemented in a 0.18 μm CMOS process with a PMOS input stage, was developed, achieving an input-referred noise density of approximately 26 nV/Hz^1/2 at 20 kHz. To investigate the impact of circuit architecture on noise performance, three pre-amplifier configurations, namely voltage-mode amplifier (VMA), charge-mode amplifier (CMA), and instrumentation amplifier (IA), were realized using the proposed op-amp and evaluated with an electrical model of piezoelectric hydrophones. Comparative results highlight the noise performance of these topologies and provide a direct assessment of their relative effectiveness for low-noise SONAR receiver applications.