A Buffered Single-Supply Charge Amplifier for High-Impedance Piezoelectric Sensors

This paper presents a differential-input, differential-output charge amplifier topology built with discrete, commercial components. The amplifier is designed to interface high-impedance ultrasonic sensors made of piezoelectric polymer, with a required bandpass of at least 100 kHz to 1 MHz, and needs to operate from a single 5-V supply. The performance and tradeoffs of the proposed topology are evaluated analytically and using a circuit simulator, showing a charge-to-voltage conversion gain in excess of 240 dB[V/C], while maintaining an input impedance lower than 100 Ω. Simulations and measurements of a prototype implementation are presented.