Charge amplifier

The amplifier offsets the input current using a feedback reference capacitor, and produces an output voltage inversely proportional to the value of the reference capacitor but proportional to the total input charge flowing during the specified time period.

High quality charge amplifiers allow, however, quasistatic measurements at frequencies below 0.1 Hz.

Special low noise cables with a conductive coating of the inner isolation have been developed to minimize such effects.

Charge amplifiers are also used extensively in instruments measuring ionizing radiation, such as the proportional counter or the scintillation counter, where the energy of each pulse of detected radiation due to an ionising event must be measured.

Further applications are in the readout circuitry of CCD imagers and flat-panel X-ray detector arrays.

The amplifier is able to convert the very small charge stored within an in-pixel capacitor to a voltage level that can be easily processed.