The MGPA electromagnetic calorimeter readout chip for CMS

The multiple-gain preamplifier (MGPA) is a three-gain channel 0.25 μm CMOS chip matched to the noise and linearity requirements of the electromagnetic calorimeter for the Compact Muon Solenoid (CMS) experiment. A choice of external feedback components to the first-stage amplifier allows the chip to match the different full-scale signal and noise requirements for both barrel and end-cap regions of the detector. For the barrel (end-cap) application the noise is less than 10 000 (3,500) electrons at a peaking time of 40 ns and an integral nonlinearity of approximately ±0.1% full-scale is achieved for all three gain ranges. Details of the design and performance are presented, including measurements of nonlinearity, pulse-shape matching, noise, and radiation tolerance.