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 read-out periods reduces the dead time of the HX2. The IC has a signal-to-noise ratio which is 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