Low noise differential charge amplifier for measuring discrete charges in noisy and corrosive environments

摘要

A low noise differential charge amplifier circuit for measuring discrete (e.g., pico coulomb) charges in noisy, elevated temperature and corrosive environments. An input stage of a differential charge amplifier circuit includes a twisted and or untwisted two pair cable with a grounded shield. One twisted and or untwisted pair can be connected to a sensor and a first charge amplifier and a second twisted and or/untwisted pair can be connected to a sensor electrical equivalent impedance circuit and or kept open and a second charge amplifier. The output from the charge amplifiers can be directed to a differential amplifier in order to provide an amplified sensor signal without external noise signal mainly from power supply mains. The differential amplifier and the charge amplifiers can include an auto offset correction circuit to reduce errors due to offsets.