HX2: a 16-channel charge amplifier IC for the read-out of X-ray detectors

RAL Microelectronics Group has developed a 16-channel multiplexed charge amplifier IC (HX2) for the read-out of Cadmium Telluride X-ray detectors. The IC has been incorporated into a prototype X-ray imaging system intended for non-destructive production line monitoring. The HX2 contains an array of 16 integrating amplifiers, each with a 10 pF feedback capacitor, and a dynamic range of 20 pC. The integration period can be varied over the range ~5 μs to ~100 ms. In order to extend its range of applications, HX2 was designed with two modes of operation. In the first mode, the integration period is followed by the read-out period where the 16 channels are multiplexed onto an analogue output bus. The next integration period starts when this read-out has finished. In the second mode, the read-out of the voltages from one integration period takes place during the subsequent integration period. This overlapping of integration and readout periods reduces the dead time of the HX2. The IC has a high signal-to-noise ratio (typically above 10000:1), and is suitable for the high-resolution read-out of other detector systems, such as photodiode arrays. The dual-mode operation allows it to work with detectors producing either continuous or pulsed currents