An 8 channel GaAsIC front-end discriminator for RPC detectors

Although not traditionally considered for particle detector readout, circui t solutions based upon GaAs IC technologies can offer considerable performa nce advantages in high speed detector signal processing: highf(T); devices, such as the GaAs MESFET, allow the realization of front-end tuned amplifie rs and comparators with the same detector time resolution. Such a feature i s well-suited for RPC particle detectors, characterized by short pulse dura tion and constant shaping responses. A new design procedure shows the suita bility of high speed narrow band GaAs amplifiers as voltage-sensitive input stages of front-end discriminators to perform the required voltage amplifi cation for the following comparator, ensuring, at the same time. SNR optimi sation. high gain and low power consumption. As an application of the propo sed approach, a full-custom analog chip has been designed and realized usin g 0.6 mu m GaAs MESFET technology from Triquint foundry. Eight channels of a front-end discriminator composed of a tuned voltage preamplifier followed by a high speed comparator have been realized with a resulting die size of 1.5 x 2.3 mm(2). The chip turns out to be very stable, featuring high volt age gain(> 1000), high gain-bandwidth product (10(11)) and low sensitivity( similar to 50 mu V), fast rise time (1.5 ns) and a power consumption of 25 mW per channel. It has been successfully tested as front-end stage in RPC t rigger detectors. (C) 1999 Elsevier Science B.V. All rights reserved.