5.1 Front-End analogic cards (SBBC)

5 Electronics, DAQ, Power

5.1 Front-End analogic cards (SBBC)

In order to optimize the performance of the analog electronics and reduce the noise, we have decided to position this part of the electronics as close as possible to the source of the signal (the PMT). The pulse (charge Q) of the PMT is integrated on an operational amplifier (AD8001) with a feedback network such that it has an exponential shaping behavior. The signal then enters a comparator (MVL 108 LeCroy) which produces a standard pulse whose length is proportional to log(Q). This signal is typically 200 ns for 2x106 electron charges which corresponds to a single detected photoelectron. Then, a line driver chip (DS90C031, National SemiConductors) feeds a shielded 100 W twisted pair cable leading to the digitizing card located in the AMS electronics crates. Each of the SBBC cards has two channels, each of which is connected to two PMT's. Therefore, there are four SBBC cards on each of the ten full-size modules and two SBBC cards in the half-size module. Figure B-1 in Appendix B illustrates the design of the SBBC card to be used in ATC.

Issue: Draft - Revision: 04 - Last Modified: 20 April 1997