A CMOS INTEGRATING AMPLIFIER FOR THE PHENIX RING IMAGING CHERENKOV DETECTOR

A CMOS integrating amplifier has been developed for use in the PHENIX Ring Imaging Cherenkov (RICH) detector. The amplifier, consisting of a charge-integrating amplifier followed by a variable gain amplifier (V GA), is an element of a photon measurement system comprising a photomu ltiplier tube, a wideband, gain-of-10 amplifier, the integrating ampli fier, and an analog memory followed by an ADC and double correlated sa mpling implemented in software. The integrating amplifier is designed for a nominal full scale input of 160 pC with a gain of 20 mV/pC and a dynamic range of 1000:1. The VGA is used for equalizing gains prior t o forming analog sums for trigger purposes. The gain of the VGA is var iable over a 3:1 range using a 5-bit digital control, and the risetime is held to approximately 20 ns using switched compensation in the VGA . Details of the design and results from several prototype devices fab ricated in 1.2 mu m Orbit CMOS are presented. A complete noise analysi s of the integrating amplifier and the correlated sampling process is included as well as a comparison of calculated, simulated and measured results.