A monolithic analog multiplexer for the ALEPH electromagnetic calorimeter adapted to operation of LEP at high luminosity

The hybrid analog multiplexer, currently in use on the ALEPH electromagnetic calorimeter experiment at LEP, is a variation of a previously described system which was designed for 4-bunch operation of LEP, corresponding to a beam crossing period of 22.5 μs, and is not compatible with the proposed 36-bunch operation. The system described will operate with a beam crossing period only slightly longer than the trigger delay time and at counting rates greater than 10⁴/s per channel without sacrificing the ease of calibration of the previous system. Calibration depends on capacitance ratios and not on their absolute values. Since there are five capacitors per channel, as opposed to two in the previous system, it was considered essential to resort to MOS technology to assure accurate capacitance ratios. Monolithic technology also permits optimization of switch sizes to minimize injected charge. The integrated circuit and its performance are discussed